CMX Release Notes:
After upgrading to Cisco CMX Release 10.6.3, the Cisco Prime Infrastructure stops displaying clients on the Cisco Prime Infrastructure map. This is due to the deprecation of V1 and V2 client API calls in Cisco CMX Release 10.6.3. Cisco Prime Infrastructure Release 3.8 and older versions use V1and V2 API calls to CMX to get the client information and hence it fails. To work around this issue, in the Cisco Prime Infrastructure Release 3.9, there is an option to specify the Cisco CMX V3 API credentials while adding Cisco CMX in Cisco Prime Infrastructure and thus Cisco CMX Release 10.6.3 works with Cisco Prime Infrastructure Release 3.9.
login to CMX via SSH / Console
create API user + password:
cmxos apiserver user add
In Prime go to:
Services / Mobility Services / Connected Mobile Experiences
and add API User + Password to the CMX configuration
This works for me!