Your confusion probably springs from the fact that these same folks found your same humor enjoyable just a short time ago. But that’s the thing about people: we change.
Events in our life can alter us. We continue to grow older, developing new tastes.
If your friends’ humor is changing, do one of two things: alter your jokes and stories to accomodate. Or hang around a new group of friends.
You also may want to explore why you feel such a need to entertain them.