Materials using custom shader appearing purple when building the game but look fine in the editor

Hey, I am currently making a game using the URP Render Pipeline in Unity version 2022.3.20f1. I recently installed a 3rd party toon shader (GitHub - Delt06/urp-toon-shader: 🌔 Toon shader for Unity's Universal Render Pipeline.) and everything works fine in the editor, but when I build the game all materials using the toon shader appear purple.

When playing in the unity editor: (ignore the “New Text”)

When playing in the build version of the game:

try adding it to always included shaders in the settings

Also check the Console for any warnings or errors after the build finishes. Sometimes a shader can’t compile for a target platform.