You figured it out!!!!
I'm not using a laptop but I am using multiple displays on my windows 10 desktop. And moving Calibre to the monitor that Windows identifies as "1" allows the e-book viewer to open. This is very interesting because it's the second application I've had this problem with. The other being Ultimaker Cura. I wonder what Microsoft did?
But now I have a different problem. I tested 2 books. One is AZW3 format. Size 600K. First attempt to open it took 1 minute 53 seconds with the message "preparing for first read". I closed it and reopened it. This time it said "loading book please wait" and it took 2 minutes 53 seconds. Yup...a full minute longer.
So then I tried a mobi format book. Also around 600k in size. This one took 25 seconds to load the first time and 2 minutes and 28 seconds the second time.
Those times are really excessive for small books.
I'm running the latest Calibre 5.12 (64 bit). And the only plugin I have is deDRM from apprentice alf. Of the 2 books I tried, one had the DRM stripped. The other never had DRM.
Windows 10 Pro, 64 bit, Intel i7-6700k, NVIDIA GeForce GTX 960, 16G RAM, BitDefender AV