if I had to guess here, I was thinking that it might be a cookie issue but you mentioned that you attempt a login in private mode and different browsers...

Do you have a copy of the UBB.threads Test Script installed? It should display any potential issues with your hosting environment if it detects any... Are the paths and URLs all set correctly in your includes/config.inc.php file? What do you have set as your cookie prefix?

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
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