5100 nex back up camera

[Spandakis]

I purchased an 08 sequoia that came with the avic5100nex. When I purchased the vehicle the reverse camera worked. I went and set my phone up to the unit and pushed some buttons, now no back up camera. I've gone through the settings, back camera input is on reverse gear setting is on battery, I just get a black screen and the message the video may appear reversed. I took the vehicle to a stereo shop and they "checked" it out and tell me my rca connections in the back of the unit are bad and I need to get the 7100.... so I left. Thank you all in advance for any insight.