I believe that if you think an idea is funny, but it's not getting laughs, then most likely it's funny, but it's just missing an element that is needed to trigger the laugh.
In my classes, part of what we study is WHY people laugh. What triggers that?
When you understand that at its most intrinsic level you can begin to make changes to a joke to take it from a semi-chuckle (because it's a funny idea) to a triggered laugh because it a funny joke.
Here's an example: