Arduino can't find a .h file

No idea if this is the right place for this, but here goes…
I’m making a very basic project, nothing fancy, literally copied right from the instruction book. I clicked Verify to see if I messed anything up, and I got this

Arduino: 1.8.8 (Windows 10), Board: "Arduino/Genuino Uno"

ColoredLight:3:31: error: Adafruit_NeoPixel.h: No such file or directory

compilation terminated.

exit status 1
Adafruit_NeoPixel.h: No such file or directory

Invalid library found in C:\Users\<username>\Documents\Arduino\libraries\kosmobits_archive: no headers files (.h) found in C:\Users\<username>\Documents\Arduino\libraries\kosmobits_archive
Invalid library found in C:\Users\<username>\Documents\Arduino\libraries\kosmobits_archive: no headers files (.h) found in C:\Users\<username>\Documents\Arduino\libraries\kosmobits_archive

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

The code is this

void setup() {
  
#include <Adafruit_NeoPixel.h>
#include <KosmoBits.Pixel.h>
KosmoBits_Pixel pixel;

//These vars are set by the .h files above
//int red = 0;
//int green = 0;
//int blue = 0;
//int brightness = 0;

}

void loop() {
brightness = 50;

//red
red = 255;
green = 0;
blue = 0;
pixel.setColor(red, green, blue, brightness);
delay(500);

//green
red = 0;
green = 255;
blue = 0;
pixel.setColor(red, green, blue, brightness);
delay(500);

//blue
red = 0;
green = 0;
blue = 255;
pixel.setColor(red, green, blue, brightness);
delay(500);

}

Did I mess anything up? I can see the .h file where it’s supposed to be, but Arduino can’t find it.

MaganiaSoulHeart:
I can see the .h file where it's supposed to be, but Arduino can't find it.

Which .h file?

Where do you see it?

Sounds like the .h file isn't actually where it's supposed to be, but rather where you incorrectly think it is supposed to be.

DrAzzy:
Sounds like the .h file isn't actually where it's supposed to be, but rather where you incorrectly think it is supposed to be.

I put it in all the library folders for Arduino I could find, just to be safe, and the first #include worked, but now the second one doesn't work!
Could the problem be that I accidentally opened a .h file in Notepad and it always opens it in Notepad?

EDIT: I moved the .h file out of a subfolder and Arduino found it? Does Arduino only go so far into the files for .h files?

MaganiaSoulHeart:
I moved the .h file out of a subfolder and Arduino found it? Does Arduino only go so far into the files for .h files?

Yes. If the library is in 1.0 format (doesn't have a library.properties file), the Arduino IDE will only check the root folder. If the library is in 1.5 format (has library.properties), the Arduino IDE will check in the src subfolder of the library folder.

A typical user should not need to worry about this at all. If you install the library via the Arduino IDE's Sketch > Include Library > Manage Libraries or Sketch > Include Library > Add .ZIP Library, the library will automatically be installed correctly. Only a more advanced user should ever be manually moving library files around.

More information:
https://www.arduino.cc/en/guide/libraries

Try to make your own .h file