Right Joy-Con only works when console is charging

I opened it up to switch the shell, so all of the electronics have been taken out of the original shell and moved into the new one. Now the right Joy-Con will not work unless it is connected to console on handheld mode and only when the Switch is connected to power. I have tried a known working battery with this Joy-Con so I’m pretty certain this isn’t a battery issue. Anyone know why this may be and how I can fix this issue?