Thanks for the message @RRUte. I just noticed this same problem while working on the new version of the app. Apparently a recent update to the site or server broke this feature. I’m working on it. Until that’s fixed you can use the website version to update your avatar. Click on your name or avatar to go to your profile. In your profile, click the profile link, then select “Change Profile Photo.” Give that a shot.
I’ll post an update when this issue is fixed.