Ok, it is a simple concept that I think many people forget. Things work in a dream because you think they will work. This goes for occurrences, locations, control, and yes reality checks as well. The reasons certain reality checks don't work for everyone is because people are different and will have different levels of confidence for the success of a reality check. That said, do you do reality checks in real life (even occasionally)? When you do these reality checks, are you honestly questioning reality, or merely going through a pre-defined motion that has become a habit? There was a point where I was doing reality checks quite often, but because it had become a habit and less of an actual question of reality, this lackluster attitude would carry into my dreams so the reality checks would not work. (because I subconsciously expected them to fail like in real life)

So to make a long story short, make sure you are actually doubting reality when you try them in real life. Expect them to work, visualize them working, if they don't work, try to force it a little to make extra sure. Spend a minimum of 30 seconds trying to make it work before giving up, and if this was the problem, you should be well on your way.