Your guess is as good as mine! I've been dealing with the hell that is anhedonia since I was 15. When it was at it's worse I could dip my hand in freezing cold water for minutes and not feel anything, so please, when you find the answer LET ME KNOW.
Lol but seriously, here's a video I found of a guy sharing what works for him.
Personally, I haven't been able to try what he recommends (due to my shit circumstances) but I hope you find it helpful (: