Apple ID and password "incorrect," but isn't
I need to upgrade my software from Yosemite to Big Sur (2013 Macbook Air), but my Apple ID login keeps telling me I have the wrong password. Reset it several times, same error. This computer used a different Apple ID in the past, and I'm wondering if that is the issue? Is it confused, and how can I help it? I'm able to log in online (here and in iCloud). The problem is local and I haven't been able to upgrade for several software upgrades because of it. Now I'm so behind that Chrome isn't supported. Help!
MacBook Air 13″, macOS 12.2