When plugging in a new radio an error returns showing "unknown device", and fails to add the new serial number

The device programmer log file will show the following error "SFC_RM_MAXLIMIT_LICENSE"

Log file location depends on DP used:
C:\ProgramData\Motorola\CommonCPS\APX RM Device Programmer\<current date>\proxy_debug.log

or
C:\ProgramData\Motorola\CommonCPS\Astro POP25 RM Device Programmer\<current date>\proxy_debug.log
 

All of the 100 provided/free RM application licenses have been used

APX RM using over 100 radios, or a user who has added additional licenses, and maxed out the number available

Purchase and then add additional radio application licenses through the RM client settings - manage - licenses - application licenses.
-OR-
Remove unused radios to free up additional licenses.