Some two-pin cables for Baofeng/Kenwood will NOT work. The GP88S requires a specific resistor network inside the cable (often 10k ohms on the TX line). If your cable works for a UV-5R but fails on GP88S, the issue is the cable, not the software.
You need a specific cable that connects the computer to the radio's speaker/microphone socket or a battery-style connector . motorola gp88s programming software
For users unable to source legacy CPS, consider: Some two-pin cables for Baofeng/Kenwood will NOT work