Good evening. I have a new to me 2021 GMC Sierra 1500 at4 with around 39,500 miles. On the dic I'm getting check trailer lights. I can dismiss the messages but my 7 pin plug does not work. I replaced it the 2 modules above the spare tire with no luck fixing it. I was hoping for some help before I take it to the dealer. Thank you in advance and I love this site.