USB devices usually require power. The GP32 USB socket doesn't provide power.
I've just bought an Ericsson Chatboard on Ebay. It cost me less than two pounds. I've found pin assignments on the 'net... 3v, Gnd, TX, RX and "S". Connect the 3v, GND to the GP32, TX to TX1, RX to RX1 and 3v to S...