> Any other idea ? Yes. As Kevin indicated, I would start with your 'attr_match_list'. On your testing/development RT instance, try running it with just:
'attr_match_list' => [ 'Name' ], and see if the user can log in. Tell us what happens. Also, judging from the "Couldn't create user myuser : Email address in use" error I would guess some other user has that email address. Try searching for users with that email address in RT and tell us what you find. Good luck. Nathan