Bingo! Thanks so much Daniel for your tips there. It was the third point in 
your email below which worked. Simple, insert cord first, wait ten seconds, 
then plug on the drive. It mounted straight up after this. So simple too.

Many thanks to all of you who had suggested some things to try as well. 

That is one for the archive for next time around - if it happens.

Now I can copy back the Photos libraries to the drive for re-use.

Kind Regards

Pete

> On 11 Mar 2019, at 5:43 pm, Daniel Kerr <wa...@macwizardry.com.au> wrote:
> 
> Hi Pete
> 
> Couple of other things you could try as well to just “Reset” it.
> 
> Try a PRAM reset.
> https://support.apple.com/en-au/HT204063
> (Basically restart with the Command-Option-P-R keys held down).
> 
> If still no success, try an SMC reset - 
> https://support.apple.com/en-au/HT201295
> (Basically, unplug everything except the power cable. Shut down the computer. 
> Hold down the left hand side Shift-Control-option-power button at the same 
> time. Hold for about 10 seconds. Then start like normal.
> 
> If no success still,.
> unplug the USB cable from the drive itself. Plug the cable into the computer. 
> (without the drive). Then after 10seconds, plug the USB drive into the USB 
> cable and see how it goes.
> 
> Had success with a “non mounting drive” with some or all of those.
> 
> Kind regards
> Daniel
> 
>  Sent from my iPhone XS 
> 
> ---
> Daniel Kerr
> MacWizardry
> 
> Phone: 0414 795 960
> Email: <daniel AT macwizardry.com.au>
> Web:   <http://www.macwizardry.com.au>
> 
> 
> **For everything Apple**
> 
> NOTE: Any information provided in this email may be my personal opinion and 
> as such should be taken accordingly, and may not be the views of MacWizardry. 
> Any information provided does not offer or warrant any form of warranty or 
> accept liability. It would be appreciated that if any information in this 
> email is to be disseminated, distributed or copied, that permission by the 
> author be requested. 
> 
>> On 11 Mar 2019, at 2:05 pm, Peter Crisp <petercr...@westnet.com.au> wrote:
>> 
>> HI Neil, yes I had also sought to rule out the USB ports as being suspect 
>> and I inserted a known good USB thumb drive to Jo’s MBP which immediately 
>> mounted per normal. So I believe the USB ports are fine it is just the 
>> relationship with this particular HDD external drive and the MBP is where 
>> the issue lies.
>> 
>> I did a Basic erase and reformat of the drive which still resulted in not 
>> being recognised and am now in the process of doing a Secure erase - takes a 
>> fair bit of time. I’ll have to wait for that to finish. If that is 
>> unsuccessful, I will try the recent tip Ronni sent with the System 
>> information screen and Activity monitor. 
>> 
>> Will keep persevering with this thing and advise further results.
>> 
>> Regards
>> 
>> 
>> Pete
>> 
>>> On 11 Mar 2019, at 1:29 pm, Neil Houghton <n...@possumology.com> wrote:
>>> 
>>> Hi Peter,
>>> 
>>> In your original post you said that the disk is not recognised by your 
>>> wife’s MBP but that it mounts fine to your own MBP and content is seen as 
>>> expected - so just a couple of thoughts:
>>>    • Is it possible that the original problem was either caused by or 
>>> resulted in an actual problem in the USB port(s)/bus on your wife’s MBP – 
>>> have you since connected another, known to be good, external drive to this 
>>> MBP and does everything work OK.
>>>    • Assuming you prove that the USB ports are both OK on your wife’s MBP, 
>>> try mounting the disk to your own MBP again and, assuming it still mounts 
>>> OK, run the disk repair routines from your MBP (at all levels) and see what 
>>> errors it can find and fix.
>>> To me, it seems like you are assuming that you have a problem with the 
>>> external drive caused by the disk being ejected improperly – and I am not 
>>> ruling out that possibility - however the fact that the disk seems to be 
>>> working fine on your MBP but cannot even be seen by Disk Utility on your 
>>> wife’s MBP seems strange to me. I would definitely want to first rule out 
>>> any USB problems on your wife’s MBP (step 1 above). Assuming that all 
>>> checks out, step 2 might let you “sneak up” on any problems with the actual 
>>> drive ;o)
>>> 
>>> 
>>> Just a thought.
>>> 
>>> 
>>> Cheers
>>> 
>>> 
>>> Neil
>>> 
>>> 
>>> 
>>> From: <wamug.org.au-wamug-boun...@lists.wamug.org.au> on behalf of Peter 
>>> Crisp <petercr...@westnet.com.au>
>>> Reply-To: <wamug@wamug.org.au>
>>> Date: Monday, 11 March 2019 at 09:44
>>> To: <wamug@wamug.org.au>
>>> Subject: Re: Disk not recognised
>>> 
>>> Hi, I’ve been continuing to attach and wait for the drive/volume to mount, 
>>> no mount showing on desktop or in Disk Utility. Numerous attempts at this 
>>> in both USB ports - still nothing showing. 
>>> 
>>> I decided just for safety I would make a copy of the two Photos Libraries 
>>> (~500GB total) on this drive over to my external drive and make sure 
>>> they’re not corrupted. That finished overnight and this morning they open 
>>> up fine on my MBP and all photos/videos present in both libraries. I turned 
>>> off TM for my MBP in the mean time during this process. 
>>> 
>>> Whilst I haven’t done this yet. I was thinking I will just erase and 
>>> reformat the drive, copy the library files back and then reconnect. No big 
>>> deal with this except I am certain Time Machine will see it all as new file 
>>> path (reformatted drive) or files and then create another ~500GB into the 
>>> backup file for what is unchanged data. 
>>> 
>>> The alternative to this is to erase/reformat the drive and then restore the 
>>> library’s files from Jo’s TM backup sometime prior to the fault occurring 
>>> Saturday eve. I think TM would then set about backing it up again so same 
>>> outcome. 
>>> 
>>> Before I go down this path, any last comments about how I could recognise 
>>> this drive on Jo’s MBP? Any commands in Terminal that might help?
>>> 
>>> At least WCE followed through yesterday, one good outcome for the 
>>> weekend... Dockers did look good for the first half.
>>> 
>>> Regards
>>> 
>>> 
>>> Pete
>>> 
>>> On 10 Mar 2019, at 3:23 pm, Ronni Brown <ro...@mac.com> wrote:
>>> 
>>> Does anything appear under ‘external’ in Disk Utility left column?
>>> 
>>> 
>>>  Ronni Brown’s iPad Pro 12.9-inch 256GB 
>>> 
>>> 
>>> On 10 Mar 2019, at 2:50 pm, Peter Crisp <petercr...@westnet.com.au> wrote:
>>> 
>>> Just had a quick look with Disk Utility. When the USB is plugged in, 
>>> nothing appears down the left side of DU. No volume represented at all - 
>>> not even greyed out.
>>> 
>>> Regards
>>> 
>>> 
>>> Pete
>>> 
>>> On 10 Mar 2019, at 2:28 pm, Ronni Brown <ro...@mac.com> wrote:
>>> 
>>> The volume of the external drive will be grayed out until the Disk is 
>>> ‘verified’ and then ‘Repaired’. But the external drive should show as it’s 
>>> the volume which hasn’t been ejected correctly.
>>> 
>>>  Ronni Brown’s iPad Pro 12.9-inch 256GB 
>>> 
>>> 
>>> On 10 Mar 2019, at 2:17 pm, Peter Crisp <petercr...@westnet.com.au> wrote:
>>> 
>>> Ok ha ha ha thanks for that Ronni. I had opened Disk Utility but the volume 
>>> doesn’t show in the first instance to attempt a repair. But I will keep 
>>> trying to get it to mount.
>>> 
>>> I am off to Rushton Park to see the WCE V Dockers Derby soon and will sit 
>>> down with a wine to have a crack at it again.
>>> 
>>> Regards
>>> 
>>> 
>>> Pete
>>> 
>>> On 10 Mar 2019, at 1:49 pm, Ronni Brown <ro...@mac.com> wrote:
>>> 
>>> Hi Peter,
>>> 
>>> This will take many try’s, but persist with it. You might need a glass or 
>>> two of wine or beer Peter.
>>> 
>>> 1. Connect the external drive to your wife’s MacBook
>>> 2. Open Disk Utility > in the left column, select the volume of the 
>>> external drive
>>> 3. Click ‘Repair Disk’ 
>>> You will keep receiving the Error: ‘Disk Utility can’t repair this Disk etc 
>>> because the drive has not been ejected properly’
>>> But keep hitting Repair Disk until it eventually runs correctly through and 
>>> completes the process of repairing the drive.
>>> 4. Disconnect the Drive correctly and remove it from the USB port.
>>> 
>>> Let’s know if it gets rid of the Notification notice when the external is 
>>> connected again to the MacBook.
>>> 
>>> Regards,
>>> Ronni
>>> 
>>>  Ronni Brown’s iPad Pro 12.9-inch 256GB 
>>> 
>>> 
>>> On 10 Mar 2019, at 12:22 pm, Peter Crisp <petercr...@westnet.com.au> wrote:
>>> 
>>> Hi folks, last night my daughter inadvertently when moving my wife’s 
>>> MacBook with external drive (Photos library) attached, unbeknown to her had 
>>> caused a glitch in the connection to the MBP - probably just wiggled the 
>>> USB lead. When I went to look at it later there was a notification “Disk 
>>> not ejected properly”. Of course she had nothing at all to do with it, it 
>>> was the fairies. Anyway, after that I tried to get the MBP to recognise the 
>>> external drive and it wont recognise it. It wont mount to my wife’s MBP. It 
>>> mounts fine to my own MBP and content is seen as expected. 
>>> 
>>> I have done the PRAM and SMC controller resets and numerous reboots and 
>>> still no luck mounting the drive in either of the two USB ports. 
>>> 
>>> Any tips on this please?
>>> 
>>> Regards
>>> 
>>> 
>>> Pete
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