I can't log into Microsoft via the Xbox App.

I have two aliases. I will refer to these as cat and dog. I use cat as my primary and dog as my secondary. Dog however, used to be my primary. I decided to change that though. The problem in question is with the Xbox App. When trying to log into the Xbox App it asks me to sign in. I use my cat Gmail, but it refutes it saying "That Microsoft account doesn't exist. Enter a different account or get a new one."

I then try using my dog Gmail, but it just says the same thing. I know it's not the password, and both of the Gmails are still active and in use. I also know that I can log into Microsoft and Xbox account just fine via my browser (in this case it is Opera GX). When launching the Minecraft launcher it says the following in a blue box "Minecraft Launcher is currently not available in your account. Make sure you are signed into the Store and try again. Here's the error code, in case you need it: 0x803F8001." The funny part is that I am able to sign into the Microsoft Store.

So I am stumped on why this won't work. The reason why I need to do this is to log into Minecraft, and therefore play the game. The only way I know of doing this is through Xbox. I would appreciate any help if possible.

:)