Can anyone explain why MDMA has stopped working for me?

As the title has stated: MDMA has stopped working for me. I rarely use the drug - maybe once every 3-4 months. Have the same stash that has worked very well for me in the past. I have friends that I’ve used it with and they feel the effects fully so it’s not about the MDMA itself. The medication I’ve been on is sereqoll for sleep (50 mgs) and I’m weaning myself off of it because of its long term side effects. Was on 100 mgs of sereqoll at one point and the MDMA worked perfectly fine then so I don’t think it has anything to do with the sereqoll. Any ideas on why it has stopped having any effect on me?