I got the Arduino Create Cloud working nicely with a MKR1010 and sensors on a Windows10 PC.Then after 2 weeks the debug console could not open port: com5 anymore. Without success I tried all the suggestions, FAQ's,changed USB kabel, and used a Windows10 tablet. So the MKR1010 seems at fault.
The plugin reacts on "restart" and "open com5 9600" as expected. After the errormessage, 2 ports are listed called "network", one is true, the other is false, and then they change. The one is false and the other is true. Also the question is: on which side of USB-cabel "com5" is situated? Windows10 does not see a "com5".
Have you checked Device Manager to see if the COM port for the MKR WiFi 1010 connection may have enumerated to another COM port value?
If the MKR is not see in Device Manager as a USB Serial Device, with the MKR connect to the PC, try double clicking the Reset button on the top of the MKR WiFi 1010 and see if it will enumerate in the COM port listing.
I've seen this when I had a rouge Sketch running causing the MKR go off to the weeds. If the MKR shows again in the Arduino IDE, load the basic Blink Sketch and see if it is working again.
You may have a look at this just in case the driver is not behaving
Some versions of WIN 10 HIDE the COM port selection.
Use the "SHOW HIDDEN HARDWARE" option in device manager to see them.
Also be aware that some USB chip-sets don't work well with Arduinos so it is better to plug them into a USB 2.0 port.
For the Arduinos with the same cable as the MKR's you should ensure it is both a DATA AND a CHARGE cable as some of those cables are CHARGE only and that will prevent windows from seeing the board at all.
Those USB cables also tend to go bad without a moments notice so if you have another device that uses it to connect to a computer such as a phone then try that first and make sure you can see your phone etc first before using the cable for Arduino's
Thank you for the hints. Some time ago I changed the sketch, verified and uploaded it without problems.
However I made the mistake of analogReading a digital pin, and didn't scrutinized the sketch afterwards. To much faith in the verifier. A lesson learned.