As per TV Error Codes , 7400 relates to a non-activated box. I wouldn't bet against 7402 having a similar cause, but in any case... the fix is the same. You mention "Connection error", so I'd suggest...
Call VM on 150 or 0345 4541111.
Out of interest, what sort of box do you have? Is it an older one, non-TiVo as these have recently been restricted to channels 1-5, which could possibly explain your symptoms.
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