Stuck on upload for any program other than bare-minimum

Hello.

I am using an Arduino Mega Pro 2560V 3.3V .
It is connected via USB. I am using the Arduino IDE on Windows.

Uploading a bare-minimum program is done successfully:

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}

However, when I try to upload any other program (either my own or one provided in Examples - i.e. Blink), it is stuck on "Uploading..." for a very long time until finally failing on the following error:

Arduino: 1.8.8 (Windows 10), Board: "Mega Pro 2560V 3.3V"

Warning: Board arduino:avr:mega2560v doesn't define a 'build.board' preference. Auto-set to: AVR_MEGA2560V
Bootloader file specified but missing: C:\Users\roy.mattar\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.3\bootloaders\MegaPro3.3V-8MHz-57600.hex
Sketch uses 1470 bytes (0%) of program storage space. Maximum is 258048 bytes.
Global variables use 9 bytes of dynamic memory.
An error occurred while uploading the sketch

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Selected board is ok.
Selected processor is ok.
Selected port is ok.
Selected programmer is ok - AVRISP mkll (also tried others just in case).

Has anyone run into a similar problem?

If you use a programmer to upload then you will overwrite the bootloader and any further uploads via the USB will not then work - if this is what you are trying ( you mentioned a programmer) .
You need to re load the boot loader , then put the programmer to one side and just program via the usb connection.

hammy:
If you use a programmer to upload then you will overwrite the bootloader and any further uploads via the USB will not then work - if this is what you are trying ( you mentioned a programmer) .
You need to re load the boot loader , then put the programmer to one side and just program via the usb connection.

If you use a programmer to upload then you will overwrite the bootloader and any further uploads via the USB will not then work - if this is what you are trying ( you mentioned a programmer) .

Hi Hammy.

Do you mean the bootloader is necessary to program?

hammy:
You need to re load the boot loader , then put the programmer to one side and just program via the usb connection.

By this do you mean I should burn the bootloader with one programmer selected and then program with another programmer selected?

If you want to program via a USB lead ( not with a programmer) , then you need the bootloader installed . You install it with a programmer connected to the 6 pin ICSP Connector.
Without the bootloader , the usb connection won’t respond.