Had the same issue.. I logged in some other client on browser and then it happened. I changed it again but hasn’t logged in the other client since then to confirm.
I might have tried just to save again my profile but didn’t think of that then.
nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s Damus stopped showing me my avatar
The URL is reachable: 
Did something change in Damus?
Discussion
Yeah, I was testing a lot of nostr stuff when making a bookmark collection, so same thing might've happened. But what?
Here's the list by the way:
https://letsnostr.com/t/highlighter
https://www.nostrchat.io/login