Struggling with nDisplay and poor documentation

While you have resolved your issue, please see this thread for running as a packaged build:

nDisplay not working in shipping build (but works in Development) - Cinematics & Media / Virtual Production - Epic Developer Community Forums

Basically, many of the Switchboard command line calls are actually developer only (but not all). The key ones are the -ini command line switches. You can’t utilize those switches for a packaged shipping build. Instead, you just need the DefaultXYZ.ini compiled into the project -OR- utilize one of the many XYZ.ini files utilized upon startup to tell UE to use the DisplayCluster objects instead of the standard objects when starting up the engine and the code will recognize everything.

It took me almost a month worth of work to determine this.