[Solved] Users cannot change avatar once they pick it once
I'm experiencing the same issue. I've changed my avatar picture once, and although it has changed in the "profile", it hasn't "populated" to any of my posts. This has happened after I've uninstalled the cache built-in cache plugin by wordpress. I wonder if these are related.
Solved here too. Refreshing the page with F5 was not good enough, CTRL + F5 solved the problem!