Same thing here for about a week. I have restarted, hard rebooted, unpaired/repaired controllers, cleared AI data, cleared world data, checked for software updates... you name it. I have tried everything I have been able to find to possibly fix it... nothing has worked.
I've sent two request for support and heard back nothing.
Finally, today's Google search says it is a known issue... "Unresponsive avatar edit buttons on your Meta Quest 3 are a known issue, possibly due to a recent software glitch or update. The issue of being redirected to Horizon Worlds instead of avatar options is a separate but also frustrating problem." Although all Google searches over the past week have not given this information, I guess it now has accumulated enough reports it's showing the information.
I do know they have rolled out a new update since V81, but not to everyone. I have not had the new update show up as available on my quest 3. Since support requests seem to go into an abyss never to be seen again after submitting, my best guess is it has something to do with updates.
Even though I haven't had the lasted update sent to my device, I saw the format of viewing details on apps/games in the store has changed... and that timing does correlate to when I could no longer edit my avatar.
It would be nice that a company would atleast send out statements when something has happened and things aren't working as they should and they're working on it... Instead of crickets and never replying to help request. Leaving customers, who spend Alot of $$$ on these devices and apps, etc to finally find out on reddit or some other Google search that it isn't just their device, but rather a known problem...