there everyone - I've got a strange one here. Has anyone

Hi there everyone -

I've got a strange one here. Has anyone seen an issue that suddenly appears with logging in with a multi-domain install? My users who have selected a domain option different than our "master" domain can no longer log in. They enter their credentials and are redirected to the log in screen. It's happening for the Super Admin accounts as well, the only way we are able to log into their sites is to go and edit the site and switch the domain. It's becoming a problem as over 300 of our sites are currently using a different domain and they are all contacting us for help, we're not sure what to do.. The strange thing is that I'm not aware of any changes we've made that would have caused this. We did create a custom login page, but have since disabled that thinking that it might help, but it doesn't seem to make a difference.

Any advice is very welcome, we're stumped here...

Thank you!