Can't use OneDrive on Microsoft Teams Free

I used to get an error when I went to the files => OneDrive from the left panel but after closing/reopening Teams a couple of times, I finally managed to make the sign in page appear and it's trying to login me into:

admin@MYNAME.onmicrosoft.com

and when I enter my normal password for my outlook.com email address, it says either my account or password is incorrect.

I'm signed into Microsoft Teams with my personal outlook.com Email address and pass.

why is it not working? is it not available for Free Teams?

This is also happening on Teams for web (in browser).

I have an Office 365 proplus education subscription and I have Office 365 proplus fully installed on my PC already, but on Teams I logged in with my personal Microsoft account because that's what I wanted and now Teams looks confused.