With the release of AIR 20, Adobe AIR provides support only for 64-bit Runtime dynamic library on Mac OS X.
"Error #3500" occurs when users are running the AIR app after linking the ANE with AIR project in Flash Builder or in Animate CC.

Native extension error

ActionScript error
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In the <AIR-project-name>/bin-debug folder, create the following directory path:
META-INF/AIR/extensions/com.adobe.extension
Copy the .ane contents in the com.adobe.extension directory (to obtain the .ane contents, unzip the .ane file).
The contents of this folder include catalog.xml, mimetype, library.swf, and the META-INF folder.