Hi. Looks like you haven't got the natives jar file(s) in your classpath...
In the Classpath tab add all .jar files from the previously downloaded .zip file, excluding those containing sources or javadoc in their name.
This documentation http://wiki.lwjgl.org/wiki/Setting_Up_LWJGL_with_NetBeans.html is for the old LWJGL 2.x version. In fact, the whole wiki.lwjgl.org (every page you find therein) only applies to the legacy LWJGL versions 2.x.If you follow https://github.com/LWJGL/lwjgl3-wiki/wiki/1.2.-Install#netbeans to the letter (make sure to read every bullet point three times!) then it will work. Please follow this documentation to the very letter.For example when it says:QuoteIn the Classpath tab add all .jar files from the previously downloaded .zip file, excluding those containing sources or javadoc in their name.then this really means ALL jar files (except for sources and javadocs). So, this INCLUDES the ones with "natives" in their names.
Next possible cause: You added the LWJGL library into the Modulepath. Is your application a Jigsaw (Java 9 Module System) application? You probably want to go the easier route and add it to the Classpath (instead of the Modulepath).