Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Oh, you were stacking subscriptions. That will explain it. This context is important.
You can only stack up to 5. See explanation from Microsoft here: https://support.microsoft.com/en-us/accounts-billing/subscriptions/what-happens-if-i-add-another-microsoft-365-for-home-subscription-to-my-account You will have to hang onto the codes and wait to redeem them.