saw somewhere that in order to upload a hex file to an arduino you can look at the Arduino IDE - see the command it runs, then replace the hex file with your file. this is the command I see in the output window:
C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/bin/avrdude -CC:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM5 -b115200 -D -Uflash:w:C:\Users\yossi\AppData\Local\Temp\arduino_build_696128/sketch_aug21a.ino.hex:i
I try running this from command (as admin):
cd "C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr\bin"
avrdude -CC:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM5 -b115200 -D -Uflash:w:C:\Users\foosMaster\AppData\Local\Temp\arduino_build_696128/sketch_aug21a.ino.hex:i
gives me Access is denied.
in fact, just running avrdude
gives the same error, so really - this has nothing to do with the COM port (which works fine from the IDE)
I tried closing the IDE and running again, tried rebooting - the same.
*** edit 1 ****
I actually ran this:
cd "C:\PROGRA~1\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr\bin"
avrdude -CC:\PROGRA~1\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/etc/avrdude.conf -v -patmega328p -carduino -PCOM5 -b115200 -D -Uflash:w:C:\Users\foosMaster\AppData\Local\Temp\arduino_build_696128/sketch_aug21a.ino.hex:i
since I didn't want to mess with wrapping the params - but I don't really think it matters - as the problem is running avrdude without any parameter still gives me the same error: Access is denied.