In any case the onscreen remote doesn't seem to have any effect on volume, channel selection, etc. I use RF remote for my Sat box, and I expect that I need to change it to IR, but the TV control is IR and the onscreen remote does not have any effect on the tv no matter what I press. So I expect that somehow, in spite of seeing the correct onscreen remote, that something is wrong. Any ideas?
Yes, the TV itself has nothing to do with this. Like in the real world, you are using the DirecTV remote to change channels so I am not sure why you would expect the TV to be affected. BTW, all DirecTV models use the same IR codes so it doesn't really matter what remote you select.
Which by the way does not have a valid certificate (very worrying! What's that about?) I found, "Some of these also use RF for their systems so make sure you have IR selected for the output you are using." Could someone help me understand this sentence, i.e.,
"Some of these": What does "these" refer to?
"their systems": What does "their" refer to?
"make sure you have IR selected for the output you are using": Have no idea what this means. Output of what? Using where?
As I wrote that I best explain, although you seem to understand it already based on your early comment that "I use RF Remote for my Sat box". Some manufacturers, including DirecTV allow you to use either RF or IR for your 'real' remote control to control your device. The Slingbox transmits ONLY an IR signal so if you want to use it to control your DirecTV box you are going to have to switch your DirecTV box from RF control to IR control.