Backglass that matches no table
What it means
This backglass file never displays for any table — it doesn't match the name of a table that exists.
Why it happens
With default settings, B2S matches a backglass to a table purely by exact file name, no table with that exact name means no match, however similar the names look.
How Pincab Toolbox detects it
No .vpx table with this file's exact base name exists in your Tables folder.
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).