"Even what I found funny in the past" That's what worries me.Maybe your current life situation is affecting your sense of humor. Pretty hard to laugh if you're in deep stress. I do know one element of humor is surprise. Is it possible you didn't laugh because you heard or seen it before. I know many stand ups make fun of people with mental illness. OTOH many comics show schizoprhenic and/or bipolar tendencies as per a study from a prestigious UK U. I think it was either Cambridge or Oxford. I possess a sense of humor unless I am severely depressed and/or stressed.