The tech's immediate diagnosis was that my H24 was defective. He provided me with the option of either replacing it with a H24 or H25 (they don't have older, outdated models on the truck). I told him I wanted to to stick with a H24. When he connected the replacement H24, it strangely also would not take a forced download of the software (even with multiple attempts).
The tech then went back to his truck and grabbed a H25. Within seconds, it took the software download. The tech's conclusion is that DirecTV may be having a software download feed issue with the H24.
I am glad everything worked out.
The feed issue is with your LNB though. If the Tech had changed it your H24 would have downloaded.
I also carry RF Remotes, RF Dongles, and wall mount kits on my truck.
I don't always have the latest equipment though, it's whatever is available at the warehouse.