Unable to detect monitor

Hello Jason, Thank you for reaching out to us! It will be difficult to say why it worked for a moment and stopped. Please tell me, does the monitor work correctly when connected directly into the PC? Thank you, Katarzyna

I have a very similar problem 

The old Hyundai L72D monitor with both DVI & VGA input's has worked quite happily as a monitor on my system. And it worked perfectly well when I was mirroring my MacBook Pro (2011) output to this monitor running High Sierra 10.13.6. My other external monitor an Acer AL1916W monitor with just a VGA input I've been using perfectly well as my other external monitor extended to the right of my laptop. Initially when I looked for 'extended display' it would not show in the software. Now, the monitor is not working at all. Help please? If you need any information and log files I can supply them if you tell me where to look. Background was in Telecomms engineering but this has foxed me today when my DisplayLink just arrived.

Update @19:01--> The monitor is now working via the DVI input however for some strange reason my mouse does not show itself within that monitor screen,.....Weird!!!!