There is a couple different factors that go into the avatar failing to upload file size, frames, dimensions, file type.. etc.
I personally would suggest a avatar around 190x190 or 200x200. The file size around 200-400KB. The file extension as .GIF.
Now, being said there are glitches when uploading avatars to where it shows a failure or doesn’t show that the file correctly uploaded. However, if it gives you the prompt “successfully uploaded” even if there is a glitch, it will work you just have to wait the hour.
If you’re having trouble still, shoot me a PM on Discord MAGZ#8039 and I can try and edit the file for you.