Why do I get a “No Kernels Available” or “Could not find MathLink executable” error message?

webMathematica generates these messages if it cannot locate the Mathematica kernel. A typical cause is when Mathematica is installed in a location other than the default installation directory.

First, verify that the Mathematica kernel works by starting it and running some sample evaluations like 2+2.
The KernelExecutable tag in the MSPConfiguration.xml file may be set so that webMathematica uses a specific Mathematica kernel. The MSPConfiguration.xml file is located in the webapps/webMathematica/WEBINF directory in your Tomcat layout. Nest the KernelExecutable tag inside of the KernelPool tag. Inside the tag, place the full file path to a working Mathematica kernel.