Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
The following fixed for me.
In Firefox
Menu > settings > privacy & security
Under “enhanced Tracking protection” check the button for “custom”
click the drop down menu next to Cookies and change the settings to “Cross-site tracking cookies”
Enabling cross-site tracking cookies should work for other browsers as well.
Hope it helps.