There are two reasons that this message can occur.
The first, and most obvious, is that licenses for Canon iMFPs have actually been exceeded. To resolve this you would either need to set devices as "inactive" making them unusable in the system, or purchase additional licenses.
The second reason, is that any failure of communication between the device and the Pharos EDI (on the Pharos server) will result in this message being displayed. It could be a network "glitch," an issue with the Pharos EDI not functioning properly, or anything that corrupts the data traveling between the Canon and the EDI. In these cases the message displayed is not an accurate description of the problem.
Development is currently investigating this.