Are any pins broken? (Check Description)

For starters, if you’re going to be fixing phones for a living, don’t use Amazon, eBay, Craigslsit, Wish, or AliExpress for parts. They have no quality control and they’re junk most of the time. You probably have a defective screen, especially if it’s one that had a replacement camera assembly already attached. Order parts from a reputable supplier like Mobile Sentrix, Mobile Defenders, or Injured Gadgets. You don’t need a taxID to order from them, just create an account and order what you need when you need. The connectors look fine. But there is also a known issue with the 6 plus known as touch disease. I suggest you read up on it.