Popper emulator's games or launch folder missing
What it means
The games of this emulator do not start from Popper: it looks for them, or starts them, in a folder that does not exist.
Why it happens
The emulator's folders are stored in PinUP Popper's database; they often still name the PC the database came from, or a place the files were moved away from.
How Pincab Toolbox detects it
The emulator is visible and has at least one visible game; its games folder, or its launch folder when the launch script uses it ([DIREMU] outside a comment), is a full Windows path, on a drive that is there, and it does not exist.
Check your own pincab
Pincab Toolbox is a free Windows scanner for Visual Pinball X and PinUP Popper. It finds and explains problems like this one. No account, no telemetry.
Download for freeCovered: Visual Pinball X (10.x) and PinUP Popper. Not covered: Future Pinball, Pinball FX, Visual Pinball 9 and the other frontends (PinballX, PinballY).