I could sign in (probably 40 times Friday at 3 minutes to the log-in) and Saturday it was compelled to show me a blank sign in screen. I have Win10 through an HP desktop about 2 years old with no peripherals other than  an Epson printer/scanner/fax. No changes were instituted by me knowingly overnight. After researching yesterday and today, I made the change to the config.sys file suggested in an 11-29-20 post to both Basic and Pro to no avail. 2018 and 2019 allow sign ins. I have gone through all the tools, updates, fixes, etc and still dead in the water. Time to call support I suppose.