How about testing by substitution?

Try re-using the old cables just to make sure the original set-up still works. It may just be that the digi-box or whatever has failed.

Another possibility - try a re-scan, the digi-box may have lost it's memory.

Do you still have analogue transmissions in your area? Try and receive an analogue signal by wiring the aerial directly to your TV.

Unless you're in an area with particularly poor signal strength you should be able to get some sort of signal using a set-top aerial - although a weak digital signal isn't quite so easy to detect.

Can you borrow another TV to check out on your aerial system?

Again, try the radio amateur route - we're generally a decent lot!

Very good luck...and don't get down-hearted!

John