problem uploading to Nano

So, this morning, I was happily modifying, compiling and uploading the beginnings of a new app and all was well, then, out of the blue, I get a very long (couple of minutes) delay and then the following error message.

Arduino: 1.8.9 (Windows Store 1.8.21.0) (Windows 10), Board: "Arduino Nano, ATmega328P (Old Bootloader)"

Build options changed, rebuilding all
Sketch uses 3344 bytes (10%) of program storage space. Maximum is 30720 bytes.
Global variables use 329 bytes (16%) of dynamic memory, leaving 1719 bytes for local variables. Maximum is 2048 bytes.
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x13
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x13
Problem uploading to board.  See http://www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions.

I’ve been through the trouble shooting guide with no success. I’ve went to another computer and tried to upload the blink sketch and got the same message. I swapped USB cables to one that works on another application. I even broke out a new NANO and still I get the same message.

By substitution, I have (sort of) ruled out the NANO, the computer the USB cable, and the program and even the version of the IDE (1.6.6 and 1.8.9) All of which produce the same results (above).

Any ideas?

Select Tools > Processor > ATmega328P and try uploading again.