Product Activation Required?

SUGGESTED

Late Friday - end of month....just what I don't need!

User is getting "Product Activation" Pop-up message when tried to sign-in!

Message:  "You must activate the product now to continue"

Sage50-Quantum 2019.0 

No changes have been made to Server. No upgrade.  No reason for an existing user to receive Product Activation message.  No other (known) user problems.

Fix? What would have caused this?