Unbale to Add Device - Forimanager "Probe Fail"

Hello All,   I want to add Fortigate device running version 5.2.6 to Fortimanager running version 5.4.2. (It's compatible). When I try and add the Fortitgate device to the FortiManager I get "Probe Failed" message.    Both FortiManager and Fortigate network connectivity and both can ping each other. I have Centralised Management on the Fortigate set to FortiManager and as well FMG is allowed on the mgmt Interface.   Even if I check in the logs I can see a successful connection using TCP/541 from the FortiManager to the Fortigate.

What could be the issue with "Probe Fail" ? Does anyone have faced such issue and how to overcome it ?