Rear speaker not working

I installed aftermarket speakers in my Expedition today and although I just used electrical tape and butt connectors to make connections, everything works! Everything but my driver’s side rear speaker. I know it’s not the speaker because I wired it to the passenger side and it works. I believe it could be a connection issue because I do hear static coming from the speaker. I’m not a professional as you probably have guessed so I don’t know what it could be. Can anyone tell me why I’m not getting any music from that one particular speaker?