Yesterday I found that my SSH public key was suddenly rejected. I had not changed it myself. Upon logging in and looking at my public key in my account, I found that the text " None" occurred after the end of it. Other than that it still matched my actual public key as far as I could tell.
Removing this text and saving did not fix the rejection, but deleting the key entirely and entering it again (the same key) did fix it. I can perform git operations as before, and I did not have to create a new keypair to restore functionality.
This may happen to other users so I thought I would report it. I did find two other similar user reports through Google searching.