Reproduction steps:
1. Open project in "Original.zip"
2. Open "SampleScene.unity"
3. Select "Volume" in the Hierarchy
4. Increase Test Shader 1a Post Process effect Intensity
5. A custom Volume will be applied and become visible in both Game and Scene view
6. Re-name the Shader (don't forget to edit the 1st line of the Shader to match with the name)
7. Re-name the Script and the Class name (also the shaderPath in CreateEngineMaterial() to match the Shader from step 6 and the effect name in Post Process stack)

Expected result: same Volume effect but with different name will appear and will work exactly like the last one
Actual result: the effect does not work anymore

Reproducible with: HDRP 7.1.8 (2019.3.0f6, 2020.1.0a22)
Could not test with: 2017.4, 2018.4, 2019.2 because custom Post Process effects are not available

1. Duplicating the Script and Shader (and renaming everything accordingly) also makes the new effect not working
2. Exporting both Shader and the Script into another project also makes the effect not work there (only works in the original project)
3. You can try to reference the same Shader from another Script and choose another name for the effect and it will not work
4. Renaming files to as they were before resolves the issue