Unable to log into iCloud on my Mac

When I log in using my iCloud username and password (which is correct because I am able to log into it in a web browser) it takes me to a next login prompt which ONLY asks me for my password but it is showing the wrong username! The username it is showing is not an email address. I put my password in and it is saying incorrect password. I have no idea how to fix this issue. Please help!

I have tried logging out and now I can't log back in.