Glomex Satellite TV Dome- no signal

I got a Glomex satellite dome on my van last year and had excellent TV reception in UK and France........... as long as I avoided being on the wrong side of tall trees and tall buildings. I took the van on our first trip in early June this year and could not get a channel signal on Astra1, Astra2 or Hotbird. I approached another motorhomer with a similar dome and she told me she could not get any channels in early June either and had to have her dome replaced.

Has anyone else experienced this problem and what was the solution? I don't like the thought of having my dome removed from the roof and another one fitted.