New Outlook won't let me add my outlook email account.

(Sorry for the late reply) Thank you so much for your detailed response! This worked wonderfully, I set my primary email as the Outlook one. I hope Microsoft fixes this soon

Hi Reasonable Guy

If you look through some of the past post you will see that the problems seem to have some connection to the aliases of the outlook.com email address. In most cases the problem is directly connected to the outlook.com email address. However, in your case, I think that you will find that the email address you are having problems with is an in some way aliased to the outlook.com address. Have a play with outlook.com aliases and let the community know how you get on. This will help others and might prompt MS to do something.

Thank you!

If it's like my problem the only way to access it is to use the old outlook, the new one for some reason has licensing issues.

Here's the problem... I'm not trying to add an Outlook email account. My Outlook email account shows up just fine. Unfortunately, that's not the account that I use. My third-party email account (which I use) also shows up as if available on the left side of the screen. However, when I click to access it, a "Sign In" window appears asking for my username, which is actually helpfully provided on the sign in line. When this is entered, I get an error message that my username is incorrect. It's not incorrect, but for some reason the sign in routine will not recognize it as valid, even though up until today, old Outlook provided access to this account without so much as a hiccup.