This issue is intermittent at the moment and is believed to be related to the Discord API timing out. You can still login to your client portal account but may get an error when using Discord to sign in.
A temporary workaround is to reset your password (your email will be set as your Discord email address). Once you have reset your password you can then login using email/password.
We are aiming to resolve this issue as soon as possible however can not confirm a estimated fix due to the problem being with a third party (Discord API)