During reassembly, note the following:

The two screw posts underneath the charging port contain grounding clips. During reassembly, make sure they're still clipped in place. The clips should face towards the bottom edge of the iPhone.

Make sure the two black prongs are standing straight up. If they were bent when you removed the port, use the point of a spudger to carefully straighten them.

Remove all of the original adhesive securing the port to the frame before replacing it.