On opening outlook which until yesterday was working well I keep receiving the pop-up asking me to enter my username and password for the following server which is imap.gmail.com. The username and password are already on the pop-up but every time I press ok it simply pops back up. The same happens if I try to cancel it. While this is happening I can't use outlook to receive or send e-mails. Any suggestions on how to deal with this?

Thanks