That has to do with your post pointers, saving the place where you last read a post in a thread, which should reset themselves after a day or two to your new preference.

You can also reset your read posts progress yourself by clicking on the "Mark forums read" link on the homepage:

https://mysupportforums.org/

It's near the bottom of that page right above the "What's going on" section.

This will clear all these pointers and tell your account that you're caught up on reading all new posts in every forum. Next time you login, everything *should* be working as expected.