user47517: So I installed libraries through the Arduino interface (Sketch > Include Library > Manage Library). Then I check: C:\Users\username\OneDrive\Documents\Arduino\Libraries, and I confirm the new libraries are there.
However, when I compile I always get the error that Arduino cannot find the library, no matter which one I try to import.
I'm on Arduino 1.8.5, Windows. What am I missing?

user19409: This was a problem with using your OneDrive folder.
duskwuff wrote:

This is a known incompatibility between the Arduino IDE and Microsoft OneDrive. A fix should be available soon; in the meantime, move your Arduino sketches out of the OneDrive folder.

The issue with OneDrive folders has been resolved as of version 1.8.6.
https://www.arduino.cc/en/Main/ReleaseNotes

ARDUINO 1.8.6 2018.08.23  
[ide]  

Updated arduino-builder to 1.4.0:  
  
  
parallel build (improve compile speed)  
better reuse of already compiled files  
Windows: fixed build for sketch stored under OneDrive cloud folders



Simply update to a newer version of the Arduino IDE and you will be able to compile and upload your sketch.

47517: <p>So I installed libraries through the Arduino interface (<code>Sketch</code> > <code>Include Library</code> > <code>Manage Library</code>). Then I check: <code>C:\Users\username\OneDrive\Documents\Arduino\Libraries</code>, and I confirm the new libraries are there.</p>

<p>However, when I compile I always get the error that Arduino cannot find the library, no matter which one I try to import.</p>

<p>I'm on Arduino 1.8.5, Windows. What am I missing?</p>
 19409: <p>This was a problem with using your OneDrive folder.</p>

<p><a href="https://arduino.stackexchange.com/a/53951/19409">duskwuff wrote</a>:</p>

<blockquote>
  <p><a href="https://github.com/arduino/arduino-builder/issues/254" rel="nofollow noreferrer">This is a known incompatibility between the Arduino IDE and Microsoft OneDrive</a>. A fix should be available soon; in the meantime, move your Arduino sketches out of the OneDrive folder.</p>
</blockquote>

<p>The issue with OneDrive folders has been resolved as of version 1.8.6.</p>

<p><a href="https://www.arduino.cc/en/Main/ReleaseNotes" rel="nofollow noreferrer">https://www.arduino.cc/en/Main/ReleaseNotes</a></p>

<blockquote>
  <p>ARDUINO 1.8.6 2018.08.23  </p>
  
  <p>[ide]  </p>
  
  <ul>
  <li>Updated arduino-builder to 1.4.0:  
  
  <ul>
  <li>parallel build (improve compile speed)  </li>
  <li>better reuse of already compiled files  </li>
  <li><strong>Windows: fixed build for sketch stored under OneDrive cloud folders</strong></li>
  </ul></li>
  </ul>
</blockquote>

<p>Simply update to a newer version of the Arduino IDE and you will be able to compile and upload your sketch.</p>
