XPS 8940, P2720DC, GTX 1660 Ti no HDMI signal

I have a Dell XPS 8940 (purchased December 16, 2020) a Dell P2720DC monitor. Overnight the monitor now shows "No HDMI signal". I have tried:  unplug power & re-plug on both tower & monitor; 2. unplug all cable & re-plug on both. No luck. I have connected the HDMI-HDMI cable to my laptop and monitor works perfectly. But it won't work on the XPS tower. And since I have no display on my monitor, how can I check the drivers, etc on my tower?  HELP!  I run three companies from home using accounting software which is loaded on the Dell tower and now I cannot do any of my accounting or invoicing.  I have read multiple threads re. this problem but I don't see how I can attempt to tackle any of the suggestions if I don't have a monitor to see what I am doing.