Dell P2719HC monitor issues with usb-c

I am unable to connect my Dell P2719HC USB-C monitor to my 2018 MacBook using the usb-c connection. When I connect the monitor to the MacBook via usb-c the display is not detected and the laptop gets no power via the monitor. It is like there is no cable. (note: this monitor did work for 1 day with the usb connection) The Dell cable is usb-c to usb-c.

The Dell monitor supposedly provides 61W of power via their usb-c video connection. Yet now I am only able to use the display via hdmi. The monitor works fine when connected via hdmi but I bought this monitor because I wanted to charge the laptop whenever I am using the external monitor, hence the focus on usb-c video.

I have experimented. I can power the MacBook via the monitor when I substitute the Apple power cable for the Dell video cable. I have a couple of questions. 1) Is the Dell provided video cable capable of providing both power and video? 2) Is the Apple charging cable capable as working as a video cable? If yes, then I don't have a cable problem. 3) Anyone else have this problem?

I am suspicious of the cable.

I am asking in this forum because both Dell Tech support and AppleCare were amazingly unhelpful. Dell suggested I contact Apple for a "driver". Apple said usb-c was for data and power but not video. It was a very frustrating day. I wrongly expected tech support to be more knowledgeable than me.