You've said it, he wants to but his body won't let him.

This then suggests there in fact may be a medical reason and he really should see his doctor. There may be a more serious problem, there may be a simple solution.

Whatever you do, don't harp on it; and, NEVER feel you are responsible.

Now for a few questions to consider: how is his self-esteem? How is work going for him? Is there possibly some other outside situation or one deeply personal that is going on? Also, you haven't indicated his age which might point to a medical issue. Also, what is happening to you? Could your own age be a reason for an increased libido (many women experience an increase as they age)? How is your mental health these days? Being happy and hypomanic dramatically increases our drive.