Right Joy-Con doesn't work detached after shell replacement

Hey guys!

So a week ago I tried replacing my joy con shells. Everything worked fine for my left joy con, but after reassembling my right joy con, I realized that the 4 lights on the side don’t light up anymore. The right joy con still works when attached to the Switch, however it takes a few seconds to connect. The controller appears to not be charging as my settings, say, but I don’t know how true that is as the controller still works after a week of playing. I opened up the joy con, to see if any cables aren’t connected properly, but everything seems fine. Also I attached the joy con to the Switch whilst being open, and the lights light up when being attached, but not when detached. I hope some of you guys can help me!