Your title = error uploading avatar.
Is there effectively an error message when uploading?
Does the avatar show up in the UCP?
Does the avatar have the correct dimensions/file size?
Spelling is freeware, which means you can use it for free.
On the other hand, it is not open source, which means you cannot change it or publish it in a modified form.
Time flies like an arrow, but fruit flies like a banana.
You need to give us more information for us to be able to help you. What image did you try and upload? What was the error message? Did you get a message in your browser console? Is there any error message in your error logs on the server?
There may probably be a problem with the avatar size. You don't give much information, but if you install the following extension and make its settings, avatar size will not be a problem for both the users and you: