I have not had that exact model on the bench but I have had a few Icoms that had the Cat5 connectors on the mics at both ends and the cable pulled from the crimp point and fouled the connection point at the brass pins.

The IC-V8000 is a high power (75 watts) 2 metre radio, it will draw about 15 amps on transmit. Also you might want to make sure your antenna SWR is low about 1.5:1. If you are not receiving anything at all I suspect you may have an antenna issue and this will also effect your transmit as well as the radio will protect its self by reducing the output to almost nothing if the antenna has a high SWR. If you don't have an antenna analyzer check with another amateur radio operator they may know someone who does. Your local amateur radio club most likely will have someone who help you solving your antenna problem.