B2S plugins turned off
What it means
PuP-Packs driven through B2S plugins may not play.
Why it happens
B2S runs its plugins, PinUP Player among them, only when ArePluginsOn is 1 in B2STableSettings.xml (B2S source, B2SSettings); PinUP asks for plugins to be allowed.
How Pincab Toolbox detects it
The B2STableSettings.xml in the table's folder does not set ArePluginsOn to 1, the table has a PuP-Pack, and its script does not drive PinUP Player itself.
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).