I went to a private airfield near me today and tested Airsense on my M3C and the M2EA. Test was on 3 aircraft doing position only flights at various altitudes and distances but all passing within 750-1000 feet and less than 2 Nautical Miles away.
The Mavic DJI Fly Airsense menu was set to the most sensitive setting.

The M2EA alerted on all three aircraft. The M3C on none.

Unless the ADS-B receivers are different or there si a particular problem with the RC Pro it would seem tb be a continuing firmware issue.

DJI - please advise.

I thought it was identified that the issue is the Fly app version.  That would be consistent with your experience as the M2EA uses Go 4 right?

It was also not working properly for me on the latest version of FW, just showed the plane in the map but no warning at all - no visual or audible warning

If you downgrade the fly app it should start to work again.

M2EA uses Pilot but, yes...I agree the Fly App (current release) is the problem.

I know this is a bit old, but I've found that AirSense on the DJI RC is only reporting aircraft when 1000' away.  This is not the case when using the DJI Fly App on iOS.