Trying to add a new account to mail, get stuck on a loading screen.

Hi everyone,

So this is happening on my iMac and my Macbook Pro. I have been trying to add a Gmail account but it keeps getting stuck on a loading screen and nothing happens, even if I exit mail and such. Does anyone know how to fix this?

Thank you in advance.

Also- I didn't see a topic for the mail app, so I tagged this post as a software issue.