I'm so sorry that your sense of humour is MIA! While I understand that it may simply be a biological nasty, I would try a session of (please be patient with me here) Laughter Yoga to see if I could jump start the humour, find a way around the obstacles, rewire funny again!
ok agreeing more now. Peace and love. To clarify my earlier comment, the sense of humour is low because of poor information processing so not much to be done I am afraid. In my slumps I can still make jokes, just usually don't understand the jokes of others fast enough to catch the moment.