In the continuing saga of older "perpetual license" MS office apps accessing Microsoft 365 services here is a good article:
https://www.computerworld.com/article/3569435/microsoft-points-to-october-end-of-support-for-older-office-apps-accessing-365-services.html
"Microsoft has long played with the support of Office applications connecting to Office 365 services. Three years ago, the company said that perpetual-license versions of Office would be able to connect to Microsoft's cloud-based services only during the first half of their 10-year support lifecycle. It set Oct. 13, 2020 as the date when the new policy would take effect."....
......Mcrosoft softened the blow considerably. "We won't take any active measures to block other versions of the Office client, such as Office 2013, from connecting to Office 365 services, but these older clients may encounter performance or reliability issues over time," the Redmond, Wash. developer stated in the support document."