Double-check "B" vs "8" and "O" vs "0". Most errors are simple typos.
You have a Microsoft 365 activation code – use it once at setup.office.com , then forget it. Your real license = your email + password on Microsoft account. office 365 product key
If someone asks for your “Office 365 product key” later, just log into – no key needed ever again. Double-check "B" vs "8" and "O" vs "0"