Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
The 'Service Unavailable' error usually indicates there is a problem with the Office licence.
1
Did you purchase Office from an online retailer, and if so, what Office licence did you purchase, is that Office 2024 Professional Plus or Office 2024 LTSC?
If the Office licence you purchased is one of those two versions, then that type of Office licence is a volume licence used by large organizations, not a correct consumer licence, the best option is to contact the retailer to get a full refund, they should not be selling that type of licence to the general public.
2
If that is not the type of Office licence you have purchased, please provide some more detail on type of Office licence you have purchased.