Edit: I figured it out. It was caused by the User-Agent Switcher and Manager addon, I use it to switch user agents on one site. I switched it to whitelist mode in the settings and now it works.
Like when I try to log into chat.openai.com, I click the checkbox that I'm human and it just keeps reloading that checkbox without progressing the page. But when I open the tab in a Firefox container (which you can install with the Firefox Multi-Account container addon), it works.
I want it to work without a container open.
No it was a user agent switcher addon. But now I want to check these out ๐!
they are great to prevent fingerprinting, you can test your browser here, but will require some fiddeling e.g. enable java for content sites like YouTube or they don't work.
https://coveryourtracks.eff.org/