I'm not sure if this already has been reported & it's for the web, not the app, but if so, sorry beforehand. Whenever I try to navigate the forum within the active topics & try to look older pages, it defaults to the first page of the given forum, example: "https://portableapps.com/forum/active?page=5" where 5 can be any number, the page defaults to: "https://portableapps.com/forum/active"
I tried to see if it was maybe a cache issue in my Firefox-based browser but I tried with a Chromium-based one having the same result.
PS: I may be slow to respond.
For now, use Recent Posts instead: https://portableapps.com/tracker
If I recall correctly, I had disabled pagination on Active due to a spam attack a while back. I'll have to re-enable it.
EDIT: It's fixed now. You may need to clear cookies and site data for this site to remove it from your cache and have it working, though.
Sometimes, the impossible can become possible, if you're awesome!