Invalid License File?

Got a message today on my VirtualMin Pro server:
A problem was detected with your Virtualmin license :
No valid licence was found for your host ID f5cc502a and serial number V0JE0BDQ3WI

Nothing major has changed on that machine, except the primary IP address, but that was changed a week or two ago.

How do we fix this?

Status: 
Closed (fixed)