Adifruit Motor Errors uploading

Trying to run a NEMA 23 on Aduifruit V2. I continually get errors, such as:

avrdude: ser_open(): can't open device "\.\COM3": The system cannot find the file specified.

Have uninstalled/reinstalled
Cleaned up libraries

Please help...I just want to play with a motor already

So much missing information.

Please read this first and then you can be a little more specific.

ok, thank-you for your reply. I'm new and finding terrible inconsistencies uploading example sketches to the Arduino Uno with the Adafruit V2 motor shield. Sometimes the eample sketch "StepperTest" will upload and my motor will function and sometimes this very same code will not upload and I will get different errors. For example, the current error I'm getting:

Sketch uses 4978 bytes (15%) of program storage space. Maximum is 32256 bytes.
Global variables use 568 bytes (27%) of dynamic memory, leaving 1480 bytes for local variables. Maximum is 2048 bytes.
avrdude: ser_open(): can't open device "\\.\COM3": The system cannot find the file specified.

Problem uploading to board.  See for suggestions.

This does not make sense to have it work one moment and then have errors the next when nothing has changed. How do I get a motor consistently running properly? What am I doing wrong?

Thank you

A lot will depend on some other things.

Does the motor shield use its own power supply or is it trying to take too much from the Arduino ?

Are you using USB 2.0 ports or USB 3.0 ( 2.0 ports work better)

Can you upload every time without the shield connected ? If so then the shield is at fault.

Which stepper motor (type and model) are you using as some require more current than others and in most cases more than an Arduino by itself can supply.

Ensure nothing is using pins 0 and 1 as they are used during upload by the Arduino itself.

Thanks, again.

I have a wall mount power supply

USB 3.0 I'll try the 2.0 (thanks for the tip, I didn't know)

My Adafruit shield is soldered to the Arduino. Do you detach for troubleshooting?

I'm using a Wantalm Model 57BYGH402-2

Motor is plugged into the M1 terminal block

I should note that I've run several successful tests with this set up, however, consistency is the problem. Are these systems highly fickle and unreliable or is this operator error?

Now I haven't changed anything and get a different error after a failed upload:

c:\program files (x86)\arduino\hardware\tools\avr\bin\../lib/gcc/avr/4.9.2/../../../../avr/bin/ar.exe: unable to rename 'core\core.a'; reason: File exists

exit status 1
Error compiling for board Arduino/Genuino Uno.

What size and type of power supply ?

Those motors call for anything up to 2A per phase.
That looks like it might surpass the capability of the Adafruit board under load.
293 drivers are great for light load but have been seen to fail under higher requirements.
Most go for something a little better with anywhere decent stepper motors.

Not sure why you would actually solder a shield to a board ?
It should just plug into an Arduino UNO or similar form factor.

Make sure the jumper or trace is set correctly for the power to the Adafruit board.
Its something that has caught quite a few people out in the past.