Welcome to the forum KikiSak
Well you can forget the in-line amplifier that will only make the situation worse, if the trees cannot be
then I suggest you do a diagram with dimensions of the current installation in relation to the trees and post it here or post some photographs. Yes you are correct it is pointless paying if you cannot receive it, how long is it since the original installation was done? It could of course be many other things e.g. lnb or cabling problems but as the problem is affecting both feeds it suggests it may be something else. What puzzles me is that you say the set top box is switching itself off........Have you checked the F connectors going into the back of the stb, are there any outer braid threads shorting the feeds, is there water emerging from the F-connecters?
To be honest without a lot more information it is difficult to advise