Are these domains on different subwikis? You might be able to install the Blog Application on the second domain in this case (it seems it did not already exist there)
Otherwise ... some more information about what "it broke" means would be heplful just a guess fo mine clemens ----- Ursprüngliche Nachricht ----- Von: Keith H Am: Friday, 24.03.2017, 23:13 An: Xwiki Users Betreff: [xwiki-users] Moving the Blog doesnt work > Dear All, > > I have created one instance of xwiki to serve several domains. > > www.firstdomain.com - the top level domain > www.seconddomain.com > dev.firstdomain.com > > I wanted the blog to be in the second domain, and so I moved it and it broke. > > Why can’t each domain have a blog? > > Keith >