Windows 10, IDE 1.8.13, Elegoo UNO R3
The R3 is connected to a USB port. The serial monitor is started and the R3 is outputting data from an existing program via COM 4.
In the IDE go to Tools -> Port and it says COM4 (Arduino UNO)
Go to Get Board Info and it shows BN: Arduino Uno, and other info.
Go to Sketch -> Verify Compile and success.
Go to Sketch -> Upload and it says, the last four lines in red:
Send auto-baud
No device found on COM4
Set binary mode
An error occurred while uploading the sketch
The serial monitor continues to show output from the previous program.
Tried a second USB cable, exactly the same.
Reboot Windows 10, same thing.
Replace board with Sunfounder, change to COM5, same end result.
What should I do different?