Replaced lightening connector and now 4G and phone service unavailable

You’ll want to closely inspect the two wires that come from the Lightning Port and connect to the logic board; see Step 35 of this guide.

The actual 4G antennas are embedded inside the lower housing. The mish-mash of screws holding holding the Lightning Port also serve to connect the various embedded antennas to the flex. So start by checking the condition of the wires leading from the flex. Check the connector ends and check the connectors on the logic board. If they are damaged or improperly connected, you will not get signal. Also check to make sure you didn’t mix them up; one is longer than the other and has to connect further up the logic board.

If in doubt, re-install the original flex to see if the signal comes back, that would indicate a faulty Lightning Port, even if it charges and communicates okay.