You shouldn't use the GPS termination pin if you have two normal terminations. You might check that it wasn't used, otherwise it sounds like either one of your 2000 bus components has an issue or the GP330B has an issue. Some of the lower cost 2000 components have units where the connector key can allow the connector to be put on wrong at the back of the MFD. Double check that the key is in the right place at the back of the unit and connector. I would try another 2000 item to see if it shows on the bus, just to ensure it isn't the MFD port.