Microsoft is investigating a known issue randomly triggering "Product Deactivated" errors for customers using Microsoft 365 Office apps. [...]
source https://www.bleepingcomputer.com/news/microsoft/microsoft-365-users-hit-by-random-product-deactivation-errors/
source https://www.bleepingcomputer.com/news/microsoft/microsoft-365-users-hit-by-random-product-deactivation-errors/