Issues with the ZL

Recently I’ve been having trouble getting the ZL control to work. In the past I’ve fixed my left controller and had no issues. However, this last time I managed to get the cord undone and now when I insert it my ZL control won’t respond. While trying to fix this I discovered then I press down on the connector (I don’t know the name) the ZL starts to work. Has anyone had this issue before or know how to fix this? I really don’t want to go buy a new controller as they are expensive and I’d rather fix it myself if I can.