The same happened to me.
Try clearing cookies AND data (IndexedDB).
Discussion
Just tried (again) and no luck.
(Firefox Developer Edition on Mac)
Are you using nos2x?
These days sometimes it is giving me some glitches, I have to disable and enable it again.
I run running v1.8.2 from github.
If I'm not wrong nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 wrote a note about some problem saving the config too.