App Store has wrong email which is greyed out

I'm having an issue that I haven't been able to solve via the usual google searches.

I am logged into my Apple ID on my Macbook. When I go to update some apps in the app store it's asking me to login. My username is already in the bottom corner so I know I'm logged in but, weirdly, my dads email address is in the pop up box that comes up to login. It's greyed out and I can't overtype with my own.

I have tried to login with his password but, it says password/ID incorrect (even though it is 100% right).

The Macbooks used to be a shared device but, we all had separate accounts and I have never been signed into my dads so I don't understand why this is happening. Screenshot to hopefully explain the issue.

Any help would be great! TIA.