Lost HD signal - DirecTV

I went to bed one evening and everything was fine. My wife woke me at 0500 and said the TV was not working properly. I have been with DirectV for over twenty years and have installed the SD dishes & receivers. When I fist got HD three or four years ago I was told a technician had to do the installation. I started with one HD receiver, an HR21-200. A year or so later I had an HR24-100 added.
I got the receivers working in SD but not HD. I originally had real strong signals in Sat101 but nothing on 99(ca), 99(cb), 99(s) or 103. I replaced the LNB (SL3 4 output). I now have strong signals on 101and 99(ca). Nothing on 99(cb). Weak signals on the first 8 transponders 99(s). I have also replaced, at the suggestion of DirectV, the BBC. Two questions.
1. Are 99(ca), 99(cb) and 99(s) different satellites? What do the suffixes standfor or signify?
2. Does my problem appear to be as simple as an alignment to the Azomuth.

Thanks for any input.

This question, "Lost HD signal," is about DirecTV channels, programming, equipment, and sports.