Problem connecting factory system via Hi Level (CX-5 2016)


I recently decided to upgrade the system in my vehicle, Mazda CX5 model 2016 (none Bose system). Until now I had a Hertz Cento component + a 4-channel amplifier +sub. The original factory rear door speakers stayed and worked, and everything was connected via High Level via an Audison 4-Channel Line Output Converter.

The upgrade included construction of a new plate with the Helix DSP.3 processor + a 6-channel audio system amplifier + Xcelsus rear speakers. The connection was made through High level directly to the entrance in Helix, but we did not get any sound. We tried to connect through the Audison 4-Channel Line Output Converter and then from the Converter via RCA directly to the helix and still no sound. We did an experiment and connected RCA from the installer's system to Helix and everything works and there is sound, so we eliminated problems with the processor / amplifiers / speakers. So our problem is with the High level connection which for some reason does not transmit sound.

My installer claims that this is a problem with the vehicle, that the system probably detects that there is no speaker connection that creates resistance and therefore does not transmit the signal at all through the High level. In the previous installation the original rear speakers were connected so there was no problem connecting through the Output Converter so I had sound.

Has anyone encountered this problem? I'm not interested in replacing the head unit, and I'm interested in using the system through thehihe level connection. I would love to hear about solutions to my problem.
Thanks :)

I have attached a picture of my new plate with the new equipment :)
2019 CX-5 GTR
in all the threads I have read for the non-Bose or Bose systems for GEN1 or GEN2, I have never seen any mention of detection of resistance from the factory head unit. You and the installer seem competent enough.. I guess I'd suggest a review of the wiring.

are you reading any voltage at the place where you are getting the high level audio from the factory source?

a simple test would to put a 4ohm resister inline with the high level speaker wire before the 6 channel amplifier and see if it changes the behavior. In the same line of thought.. connect a speaker right at the high level tap.. do you get audio? If you put the rear speakers back in for a test is there audio?