In the event that inbound calls are failing in the server and when you bring up the freeswitch log it shows:
INCOMPATIBLE_DESTINATION as the error code then it is likely to be a codec issue.
What you need to do is :
1) Log into the GUI and go to your SIP profile
2) At the bottom of the SIP Profile you will find two parameters; "inbound preffered codecs" and "outbound preffered codecs"
You need to specify the codecs or negotiations will not occur.