Hi @skylogical ...
When you log in to Canvas on your computer (not your mobile device), click on the "Account" icon on the left-hand global navigation bar, and then select "Files". You will see all your personal files/folders listed on that screen. At the bottom of the "Files" screen there is a percentage bar that will show how much of your personal files space has been used. What does that say? If you are over 100%, then, you will need to remove some files that you don't need any more so that you can upload your profile picture. If you are not over 100%, then I would recommend that you reach out to Canvas Support so that they can have a look at this with you to see what might be causing the issue.
Hopefully this will help. Please keep us posted...thanks!