When I was using the Arduino IDE I suddenly lost connect to the COM 4 port. I checked under Ports (COM &LPT) and Other Drivers and it was gone.
this is a Windows 10 operating system.
Everything worked until 3/12/19. Been working without problems since I installed it in December. I did upgrade to the 1.8.8 version of the IDE recently.
I did reboot the computer. No change
Have done another reboot after restoring my C drive. problem returned
I thought it may have been when I was doing a temperature sketch on mcp9808 it started when I ran it.
But I have noticed that it has a tendency to drop off when I upload a sketch. At the present time I have used two uno that I purchased from Arduino.cc
Problem occurred on both. I also experienced the same response using the web editor.
I ran the blink sketch on both boards and no problem I have both up and running.
retiredme:
I have noticed that it has a tendency to drop off when I upload a sketch.
This isn't clear to me. Are you saying that, after the problem started, sometimes COM4 is shown on the ports list of your computer and other times it is not shown?
After I regained the COM connection, when I uploaded software it was lost again
However, after several reboots and restoring C drive to a previous version I was able to regain the link with two different Arduino unos using blink as a test.
So for now I can say problem solved.