How to write the correct shader file path?

This also stands out

  • If you get the error Can’t compile: /Plugin/<MyPluginName>/<MyFile> **not found.**Make sure to check your Plugin’s module’s LoadingPhase is set to PostConfigInit, and that there are no typo’s in the Plugin’s Shaders/ directory name.

Sorry I can’t be of more help, it looks like what you have should work.