Manhattan 5500 ci - Audio

[S47]

Just dug out my oldish Manhattan 5500 CI diseq receiver, with the intention of using it to pickup the Freesat TV channels on astra. After fitting a new LNB to the 1 Metre dish and lining it up on Astra, the receiver downloads all the channels no problem, however when I try to view the TV - the picture is fine, but the audio is just 'White noise' on all the channels
Any Ideas how to get the audio working?
I have the original receiver manual but there's nothing about correcting/adjusting the audio in the manual.
Any ideas how to sort it??
A mate suggested it may need a software update, if so any ideas how to do this?
TA
Mal