Elkhntr4evr

I recently purchased a 2021 GMC 1500 AT4 3.0L. When I first got it I was able to open both Tailgates on the Multipro Tailgate. Two days ago, the primary tailgate won’t open. I’ve tried the button inside the pickup, the button on the tailgate and the button on the key. Still not working. When I do push the button inside, I can hear a small click noise over by the fuse box area. Also, would after market rear signal lights through an error message that they aren’t working correctly? One more question also about the remote start from the key, any clues as to why it wouldn’t work, not that I’d use it. Just wondering why it wouldn’t work. More concerned about the tailgate issue. I am 63 and can’t lift things as high as I used to. Thank you for any help with this.