@ELAINEJWADDY I've added this below, as the other reply to your post was removed.
The cause is most likely a fault with your dish or cables - possibly misalignment, as you mentioned.. Unfortunately Sky no longer provide engineer support for Sky+ equipment unless you have Sky Protect, so you'll need to contact a local satellite engineer to take a look.
Alternatively now might be a good time to consider upgrading to Sky Q. Any dish or cabling issues will be addressed as part of the Sky Q installation at no additional cost to you.
