Nightmare with Directv HD 24 --- NO HDTV

Everything was perfect on my brand new Sharp Aquos LC-70LE734U when I got the bright idea to upgrade my Directv DVR from model 23, I think it was to model 24. Now I can't get 1080! Phone help from DirecTV insisted I had made the correct settings. Sharp phone help just couldn't figure out what could be wrong in the TV, so he assumes it's a DirecTV receiver issue. I'm ready to reswap the old box and eat the $194 for the new box. Any help will be greatly appreciated, thanks.

Nightmare resolved! Figured if I called DirecTV again who knows, maybe the next tech will know more. This man (Chris) immediately guessed I didn't have the B Band converters. Of course I didn't--the HD 23 didn't require them, so it didn't occur to me to order them. I swapped them out from another box not used much (he's sending me a replacement set), Chris also guessed I hadn't selected the right dish in set-up. Of course I didn't -- I chose the first one, and when that didn't work I went to the second, and when that did "work" I figured that's that. Chris knew what dishes I had and now everything is perfect. As is my custom when I get great support I spoke to his supervisor and told her what a great job Chris did.