Hi,
welcome @Anonymous.autodesk.com!
>> I select a Plot Style Table of monochrome.stb.
Verify in your print dialog that the setting for "Plot with plot styles" is active/checked.
Next verify that your monochrome style definition is the original one, not modified by anyone else.

If that does not help then go to your layout you try to print, select the viewport and look to the property window which "Visual style" is set active for the viewport and if there is a special setting for "Shade Plot".
Every visual style other than "2D-Wireframe" does it's plot-calculation by rendering ... and so converts all objects to true-color rendering. True color can't be converted by CTB/STB, so no monochrome output would be the result.
You have two options now:
- either select for the viewport "Legacy wireframe" or "Legacy hidden" (for hidden output) ... that can hold AutoCAD color index and so can be converted by STB/CTB for monochrome output
- or assign the layers (by viewport overrides) a monochrome color, then the color will be rendered in monochrome way just because of it's layer setting/overriding ... making CTB/STB even not needed any more.
If nothing of that helps then please upload your drawing + your CTB/STB file
- alfred -
------------------------------------------------------------------------------------
Alfred NESWADBA
ISH-Solutions GmbH / Ingenieur Studio HOLLAUS
www.ish-solutions.at ...
blog.ish-solutions.at ...
LinkedIn ...
CDay 2026------------------------------------------------------------------------------------
(not an Autodesk consultant)