App Refuses to Recognize a Mounted Disk Image

Attempting to run "Journeyman Project - Pegasus Prime" video game using mounted disk images of its CD-ROMs. Disk #1, which includes the program installer plus roughly 600 MB of data, works fine. When play reaches a requirement to "Insert Disk #2," my opened Disk #2 image is not recognized by the app as a disc. It appears on the desktop as a CD-ROM disc, but the program cannot see it. I presume this is because of how the app was written.

The odd thing is that the next iteration of the Journeyman Project, "Legacy of Time" does accept disk images in lieu of physical CD-ROMs. This technique also works for Riven, Obsidian, Starship Titanic, and other OS 9 video games.

Hardware: PPC PowerMac G3 Desktop (1997) upgraded with 1 Gz PowerLogic CPU, 768 MB RAM, two WD 80 GB hard drives, and the original CD-ROM player.

Software: Mac OS 9.2.2, DiskCopy versions 6.3.3 and 6.4 (have tried both, both create full CD-ROM images).

Am I doing something wrong, or is this just in the coding of the game itself?

Thanks for reading!