Reproduction steps:
1. Open the user's attached project "BugReport.zip"
2. In the Project window open "TestScene.unity" Scene and open Game View window
3. Open the "Grayscale.cs" script and comment out the namespace
4. In the Game View post-process does not appear

Expected result: custom post-process appears in Game View when enclosed in a namespace
Actual result: custom post-process does not appear in Game View

Reproduces on: HDRP 7.1.5 (2019.3.0f1), HDRP 7.2.1 (2019.3.3f1, 2020.1.0a24)
Could not test on 2017.4 due to HDRP not existing
Could not test on HDRP 10.0.0 - Preview (2018.4.18f1), HDRP 7.1.2 (2019.3.0b12) and below due to errors in the Console window related to custom post-process

Notes:
-Issue reproduces in Build
-When putting breakpoints in the Setup() and Render() methods, they never get triggered
-The volume component appears in the volume profile as expected