Hello,
I have kind of the same problem. The clicking function of the touchpad was not working ( but I could move the pointer normally using the touchpad) so I ordered a new one. I installed it personally and for a second it worked and then it stopped. I tried to switch cable between my old trackpad and the new trackpad. Nothing. The pointer is gone and the clicking function only works physically but I can’t click on anything since there is no pointer on the screen. Funny enough, I even re installed the old touchpad and the hilariously, the clicking physical function was back fixed but the the touchpad is completely useless. I tried to attach a Bluetooth mouse and follow what you have said for the other user but I do not see dell touchpad. I only have the Bluetooth mouse. Any help/suggestion?
ps: I opened the pc at least 10 times and all cable are connected. I just don’t understand. They only thing that I am worried about is if I messed up the aluminium/tin foil sheet on the top left corner of the touchpad.