Nope sadly nothing I tried worked so I ended up returning the monitor for a refund.

That seems to be it. I zapped PRAM and have not had the issue for the last 3 days.

Thank you!

If the new Monitor displays ANYTHING recognizable, it is working as designed.

Now you have to figure out what is specified, and decide what you want.

• Mission Control preferences has a “Displays have separate Spaces” setting that’s selected by default. If you deselect it:




• The menu bar and Dock appear only on your primary display.


• You can position windows to appear partly on one display, and partly on another.


• When you view an app in full screen on one display, your other displays are blank.


• Split View isn’t available.

from:

Use multiple displays with your Mac - Apple Support

.

Can it play CD's or DVD's?  Do blank disc's mount on your desktop?

I called Apple support.   We fixed it using the Terminal.  They walked me through diskutil zerodisk commands.  That's the short answer.  It's been working for 2 days now

A USB Monitor relies on USB to get the screen data out to the screen.

But its real magic is the Driver you installed. That Driver creates a screen buffer in the Mac's memory, and connects it to the USB port to paint the display.

If you are having trouble, I would look hard at the Driver installation and make sure it was OK.

I followed the instructions on this link and it worked:

https://computers.tutsplus.com/tutorials/clone-a-mac-with-superduper--cms-21474

Thanks!

Thank you I followed your suggestions and performance has improved. Inasmuch as the MacBook-Pro now boots and runs even when the battery is down. (previously it would shut down when the battery got to about 5%) . Also the battery is charging as I am working so it seems you were on the right track, its now at 91%. It seems I will have to replace the battery very soon - I am wondering if I should buy it and instal it myself or get it done at the Apple shop. I've looked at the 'how tp' video and I know I can do it  - but there may be other factors that need fixing, Any thoughts welcome. Thanks again. RS

It is possible, but not likely, that re-seating has solved the probelm.

If it were mine, I would but a label with a question mark on that DIMM. If it EVER gave me any more trouble, I would replace it in a heartbeat.

I wholeheartedly second Macjack's comments and recommendations.  Do post the Etrecheck results.