I did a forced change for everyone on the 24th due to
GDPR. It will have shown you the new Privacy Policy and the updated registration agreement. If you accept those then the software should remember your login and all should be good again.
There was a post about it
here. The software records a marker that you accepted the new policy and have read the updated registration agreement. If you agreed to both, then it should leave you alone. (Unless I make any updated changes in the future).
There was also a forced cookie acceptance policy the same day, but that is linked with the main site and will remember regardless if you accepted it on the forum or on the main site. Because that is cookie related then you will get it again on different PCs/browsers, but it's totally unrelated to forum login. The notification won't go away until you accept on that PC/browser.
The changes were necessary are with GDPR you must specifically opt in.