Please follow the guide in the yellow box about.

Thanks. I only see espre v 2.0.13 in the list of released esp32 packages. what board index url have you added to arduino 1.8?

ah, I didn't see you were using an adafruit board.

what json url are you using for that?

Normally you have an index file for each type of hardware however arduino.cc have been slowly adding duplicates for many boards to their own cores.

Please open arduino 1.8 and confirm what is in the file>preferences>board packages field.

Also confirm what is in the visual micro IDE Locations board packages field. 

Thanks

Thanks, yes I found the adafruit boards in the esp32 core.

Most of your core is being found for certain. No libraries are coming from arduino ide, the #include that can't be found is the arduino.h (that you have #included in your .ino code)

The arduino.h is not a library it is part of the esp32 core. The core also has libraries below it and your code has found them OK.

Question

A lot fails if the Arduino.h can't be found. Are you working on a case sensitive system?

does this build in a new project? ..

#include <Arduino.h>

void setup()
{

}

void loop()
{
}

Can click build on your main project again and post the output again.

Don't remove the \/ slashes just keep it as is thanks

Strange issue. Must be related to the onedrive symbolic folder. 

I see you switched on local build folder, try switching off Tools>Options>VMicro>Build In Project Intermediate. 

Then build and post the output.

If you remove the #include arduino.h does it build okay?

ArduinoOTA is a library that is supplied with the platform. It should be top of the list in Current Platform libraries.

If you use the menus to add the library they should simply add this to the code

#include <ArduinoOTA.h>