I installed an AVIN Avant 4 last fall and, in general, it's worked OK. I got in today and noticed there was no sound from any of the passenger speakers. No front, no rear. Is this a unit issue? A wiring harness issue? Thanks for advice!

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2005 X5 3.0i
2003 530i Sport (former)
2014 Audi A6 TDI Prestige (daily)
2018 MB C300 Cabriolet (wife's)