A. Enter a valid serial number on the controllers for a given device
B. Remove the duplicate IP in the network.
C. Enter a valid product ID (model) on the PNP portal
D. Match the serial number file between the controllers
E. Restore network reachability for the controller
Explanation:
https://community.cisco.com/t5/networking-documents/sd-wan-routers-troubleshoot-control-connections/ta-p/3813237