Thanks @Jim M for your support. I just tested this by removing the potential conflicting category. The filters still do not show. I also tested in on another section where I have just two simple subforums (BMW and Mini). But the filters do not show.
Interestingly, if I use fluid view on a global scale, the filters do show, as designed.
If actived per forum, it merges the topics, but now filter is displayed.
Edit: Just tested it by disabling third party apps. And it worked! So I will check which one it is...and found it: The app "Different sidebars for each forum 1.1.0" is causing the conflict.
The Cloudflare Community came to the rescue with the right pointer. The 'activity log' of the firewall rules shows the details of the triggered event. What I now did, is to allow the Invision Community user agent...This resolved the issue and login to the marketplace is no longer blocked.
There might be better solutions. Suggestions are welcome 🙂
