If the dish is not warped there is no reason you should not get most of the channels. If this was a professional installer I will presume he checked for warp and also set up the receiver correctly, and the only reason you would be getting some but not most of the channels in SET UP would be the wrong frequency for the LO on the LNB.
Since you have one G25 transponder, it will just take more tweaking, as we say, trial and success, to bring in the rest. Do not give up. Check for mast alginment. Tilting could get you one and not the other, very hard to get both.
I do have a wind-warp problem here but most people do not, and I set up my Glorystar system several times on an 8000 mile trip with almost no problems. Recheck and ask more questions. I do not know anyone who has failed setting it up yet.