Problem connecting lightning port assembly back to the board

That's an antenna cable. The trick is not to use a ton of force or you squish it. I normally use a pair of tweezers to get it lined up over the...hole..thing...connector....you know what I'm talking about. Then I use a plastic spudger or something else that isn't stiff to pop the connector back on. Don't feel bad...those things can be a pain.

If you can't get it being gentle, then line it up and press down with the side of your tweezers until it pops in. I've had some aftermarket ones where I had to spread out the outside of the new adapter just a smidge to get it to go in. Just remember that there is a tiny pin in the middle of the thing and if you bend it, you are starting over with a new adapter unless you get the thing straight, which I've never done.