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

Changing your primary alias doesn’t really affect the functionality of your Microsoft account. You can still use your personal email as a secondary alias to sign in anywhere. It just gives you more functionality if you sign into the new outlook with the @outlook.com alias.

If by "more functionality" you mean "the ability to use the app" then we are in agreement. When i use my personal email as my primary alias the app is unusable. Not in terms of inconvenience or that i have a complaint, but that it's void of functionality, i can't access the interface beyond the login screen. (Unlike every other MS product i've used). I can't add my MS account, using either my personal email address or my MS address. This is after weeks of troubleshooting every permutation of adding/removing/repair resetting/olk command line stuff suggested by in-app support, on multiple computers. When i change my primary alias back to my MS email, everything works fine, but i lose a feature - the ability to use my personal email address.

My usage of a primary alias is completely irrelevant to any other MS product i use. Stated differently, email is the only reason i'd have my personal email set as my primary alias, or even associated with my MS account. In the "old" mail app, outlook android, and outlook.com, i can set the "from" field to my personal email address rather than my MS account email. Setting my primary alias to my personal email address makes my personal email the default, so i don't have to specify it each time. In the new outlook, setting the "from" field to my personal email address is not something i can do. When i add my MS account to the new outlook (which again, i can only do when my MS email is my primary alias), my personal email address is not in the "from" dropdown.

In short, i can't use New Outlook if i have my primary alias set to something other than my MS/outlook email address, and i can't use secondary aliases in the New Outlook. I guess i'll narrow my original statement to: New Outlook is incompatible with aliases. That's the experience i'm having, anyway.

Your solution (switching Outlook versions) doesn't work, it tries adding the account, I get the "signing you in" screen and end up back at the "Welcome to the new Outlook" login.

The same account works fine in old Outlook.

Is there any update on this issue? My account still won't log into new Outlook.

Yes, I have Microsoft 365. I just opened Word and Excel. They work fine. Maybe I need to restart now? I'll try that.

Nope, restart was no help. I tried to readd the account but it still says "Already added". Since it does not appear in the list, I cannot delete it either.

Should just be in the upper right-hand corner. If it's not, maybe you don't have the right version of Office, I don't really know.