avrdude: stk500_recv(): programmer is not responding
Good question... I presume the Uno? How do you pick? I'm guessing it's just based on which "board" you have selected in the drop down?
I did "burn bootloader" and after a long time it appears to have worked. It reverted to the standard "blink" sketch that comes on new Arduinos.
I found the problem to be related to uploading a sketch (from the programmer) after burning the bootloader. How I fixed this was to NOT upload a sketch from the programmer after burning the bootloader. Remove the chip from the programmer and put it back in the UNO, then upload the sketch to it.