Backglass under a slightly different name
What it means
This table's backglass is probably already there, under a slightly different name, so it doesn't show.
Why it happens
With default settings, B2S only loads a .directb2s with exactly the same name as the .vpx. A shortened name, a version suffix or different spacing is enough to make it invisible.
How Pincab Toolbox detects it
No .directb2s has the table's exact name, and exactly one unclaimed file has the same name when case and punctuation are ignored, or the same beginning (B2S's short-name rule).
Automatic repair
Repair, included in the Pincab Toolbox licence, can fix this one for you. Your files are backed up first, and the fix can be undone.
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).