correct apple ID password refused on mac

I enter my apple ID and password and get a notification on my phone that someone is trying to login, I consent and get a verification code but neither iTunes nor the app store accept that the password is correct. Despite the fact that I have just used that very same password to log into iCloud in preferences without issue.

I've even resorted to changing my password to no avail. I'm currently on Yosemite (for some reason it install after a fusion drive rebuild) and wanted to download Big Sur from the App Store when I discovered this issue.

Any suggestions are most welcome.