Shrink it down. Make a support ticket to the staff and ask them if its of if they help you through this.

The maximum size for an avatar (profile picture) in terms of dimensions is 100 pixels by 100 pixels. Even so, in my art program, I make the artboard size as 99px by 99px because an extra pixel always seems to be added to the width and height after I export it.

If that doesn't work, possibly, you've exceeded the 75KB file size limit, uploaded the wrong image format, or simply did not select the image you just uploaded to become your current avatar.