Thanks both for your replies.
The mic is connected to the RRC control Aux/Mic jack.
The cat 5 patch lead is connected from the radio RRC Aux/ Mic jack to the radio RJ45 jack.
Everything works as it should except for the lack of audio on the TX signal
When the PTT is pressed RX audio is muted control and radio end and the radio transmits a carrier but no audio
If I plug the mic directly into the radio RJ45 everything works including TX audio so the problem is not the microphone.
73 Mal GW6OVD