Backup Camera blank with aftermarket head unit in 2015 v

I'm stumped: My reverse camera feed is black after swapping the JBL MFD for a Pioneer AVIC-W8400nex with Maestro RR interface on my 2015 v Five w/ATP.

Does the 2015+ / ATP require a signal wire to the reverse camera that woudn't be present in the earlier years or non-ATP cars?

• The reverse view worked fine with the Toyota MFD,
• The Pioneer head unit switches views to reverse mode when the car is put in reverse, so it's getting the shifter signal, but no video signal,
• Doing a similar swap (Pioneer AVH-4200nex with Maestro RR) on my 2012 v Five (non-ATP/JBL) was seamless, but that was 4 years ago,
• I've reflashed the Maestro RR twice with no change. All other functions work fine;
• I'm using the HHR-TO2 vehicle harness and the PIO1 head unit adapter pigtail, along with the "A" camera harness.

Any advice would be appreciated. Thanks!

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