I'm trying to convert a vector layer to a KML file.
Here's what the layer looks like in ArcMap-- as you can see, it has multiple polygons:

Here's my code:
<SPAN class="keyword token">import</SPAN> arcpy
arcpy<SPAN class="punctuation token">.</SPAN>env<SPAN class="punctuation token">.</SPAN>workspace <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'C:\\username\\folder'</SPAN>
mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN>r<SPAN class="string token">"PreHex272.mxd"</SPAN><SPAN class="punctuation token">)</SPAN>
lyr <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>LayerToKML_conversion<SPAN class="punctuation token">(</SPAN>lyr<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"kml_tests.kmz"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="line-numbers-rows"><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN><SPAN></SPAN></SPAN>
But it only outputs one small polygon in Google Earth:

I do not have any polygons selected. In fact, I tried selecting a different polygon and got the same result. I tried selecting all polygons and got the same result. I also tried restarting Google Earth, with no luck.
I'm using ArcGIS Desktop 10.6.1 on Windows 7.
Thanks in advance!
(Hopefully this is the right place to post-- I'm still getting used to picking which GeoNet "community" to post in. Sorry if this is not the correct location.)