Hello,
If the issue was not present before the charging port replacement, then the sudden loss of signal is most definitely stemming from the replacement. As always, before proceeding always make sure to soft reset the phone by holding home and power button simultaneously for 30 seconds. If problem is still present, try steps below.
1. You should check under the battery connector cover, if the gold antenna connector isn't plugged in, plug it in.
2. If the connector is plugged in, you need another charging port. Charge port issues, while rare, still occur. Sometimes the solder from the antenna connector on the charge port is loose, or improperly done. A new charging port should fix the issue.