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I have tried 2 new charging port replacements with the same results - No cellular service. I then put the original port back in and cellular signal returned. The phone is an or was unlocked T-mobile and using a Cricket wireless sim (AT&T). I now have the new charging port back in, the cell signal at the top of the phone shows nada with a circle in the middle. Tried to scan networks and unavailable. Any help would be greatly appreciated. Thanks in advance

There are about 3 different models of replacement charging ports for the S8. Are you using the one for the SM-G955U? Different ones will have the gold prongs and different internal wiring which connect to the antennas on the phones housing in different areas.