That error unfortunately says nothing and everything the same time.
Could be
- Filesize issue
- Filename
- Broken file / invalid file type
- Server error. Could not write or delete old avatar. Queue for file transfer is full. Port for file transfer is not forwarded. File on server is detected as virus
- more… But have no clue
Does it only happen on one server?
What server server version are you trying it?
Can you please share the image here?
