There have been a lot of topics about this error recently. It is quickest to call into 150 / 0345 454 1111 and report a TV fault. They would check out your STB for anything which could be causing the problem. Though you can of course wait until a member of the Forum Team here picks up on your topic. If you're posting from your VM broadband connection or registered to here with your VM email then they'll be able to locate your account without needing to private message you.
+Add: In general, credits are applied for a total loss of service, which went on for longer than 24 hours.
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