Thank you very much because that worked! You are right that the B Series USB Monitor APP for Mac OS Catalina 10.15.5 works for AFTER 10.5.5.
The second step is that the driver is downloaded as DisplayLink Manager and it requires opening system preferences, opening security and privacy and allowing DisplayLink Manager "to record (???) your screen."
In the picture above, it shows DisplayLinkUserAgent which is not the DisplayLink Manager that you need to check and give permission to use. (And you have to unlock and relock in order to save this permission.)
Then a restart and yes, now my ZenScreen MB16ACE will work with my MacBook Air with Catalina 10.15.5.
I called both ASUS and Apple Support and got told they just do not have a driver after 10.15.5
BUT THEY DO.
And another bonus! You can have your MacBook Air monitor, an external monitor in the monitor adaptor slot and the Asus ZenScreen MB16ACE plugged into the USB with USB-C adapter and have all three monitors working independently. WOW!!!!
Thank you for the solution!!!!!