When you subscribe to SuitePOS you are set up with a set of entitlements based off what you purchase. Example of such entitlements are terminal/device counts and modules (eg. Advanced Inventory).
Each time a full (or diff) sync is performed (at least once a day) on the device, SuitePOS checks your entitlements. If you are using modules you are not entitled to and/or have exceeded the terminal counts allowed, SuitePOS will block access until it is corrected. An error message is displayed that indicates what the issue is.