Can only log in using splashtop

Unaccountably, I cannot log into a local Windows 10, 22h2 system unless I use Splashtop.  The streamer is version 3.4.5.0 and the problem started about the time that KB5022906 was installed (March 6).  That may be a coincidence, but it was the only update since a week ago and all other updates were a month or more ago.

The system is set not to sleep and the display is set not to turn off.  The monitor does have sleep enabled.  It is a touch monitor and connects using DP & USB3.  This has all been working find since last year.  I swapped the Bluetooth keyboard and mouse for wired but it made no difference.

Pressing return or touching the screen causes the monitor screen to show the windows 10 background but the login dialog box is missing.  It is as if the PC thinks there is another monitor.  Clicking the mouse, tapping the screen or pressing return key just beeps through the speakers.  Once I make a connection using iPhone or any PC running the Splashtop client the login box shows up immediately on the remote system. The system works fine till the next morning. 

I normally access this system from my dual monitor windows 11 system. Could the windows 10 system think there is a second monitor and made it the primary?  There has only been one monitor on it since it was set up.

I do not want to uninstall Splashtop and then find I cannot log in.

=============fixed============

must be a  Microsoft problem.  I created a new "local" user and made that user administrator.  I then enabled Microsoft's remote desktop so I could log in locally if I decided to remove Splashtop. After rebooting all is working fine.  The login screen shows up due to the "blank" screen saver requiring a log in screen.  I disabled that option just to be sure.