Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
1
You mention Office and Microsoft 365, ensure you only have one version of Office installed on your PC, if there is a second version, uninstall the oldest version of Office.
2
Before performing this process, please log into your Microsoft account on this link (https://account.microsoft.com/services/) and check to ensure your Office licence or Microsoft 365 subscription is listed correctly on your account.
Open the Settings App (gear icon on your Start Menu)
Go to Apps, then scroll down to find Microsoft Office
Select that and choose Modify - Online Repair
That should fix any issues with your Office Installation.