how can I fix my Amstrad 550.033 receiver ?

I have a Amstrad 550.033 receiver running o/s 1.2S4FJ and EPG S/W v3.7.6

I am getting error message no satellite signal received although the signal test shows that I'm getting a strong signal with good quality. Any suggestions to what I can do greatly appreciated. I really don't want to pay another 65 quid to SKY. Thanks