We're aware that avatar uploads aren't working. A support question has been raised with the software maker, but no answers have been found yet (in fact, after a lot of back-and-forth, they pretty much came out stumped).
For the time being, you'll have to select one of the already-available avatars on the system. If there's a Jim-related avatar that seems to be missing, let me know, and I'll see if I can do something about that!