Interpreting the notification:

“General Information - Activated: License is not enough (X/Y)”

・X = The number of reader inputs in Monitor cast
・Y = Number of licenses activated on their serial

　1. The primary way to resolve it is to add more Door Licenses to the Serial and then update the Activation.
　2. Outside of that, if they are using EP1501s and checked the box for the "Additional onboard Reader" when they added the Controller,
　　that extra Reader Input counts against their Licenses

　　a. You can delete the controller and re-add it to Monitor cast to remove the second reader.