Be aware of the difference between CPDLC and ADS-C position reporting.
North Atlantic uses ADS only, they don't process CPDLC position reports at all. (ATC communication via CPDLC though)
In Asia and Australia CPDLC is used for position reporting.
ADS operations are normally completely transparent on most planes, if you are lucky the show you're connected, if very lucky with whom.
Feedback about outgoing position reports is often not visible to the pilot.