Undefined control sequence error on first attempt

I am using PTXPrint for the first time. After running the basic checks on my project, I followed the beginners’ tutorial for a first PDF creation, 1 John. I received the following error message:
PTXprint [2.3.20] - Error!
Failed to create: Ldm_Default_1JN_ptxp.pdf
! Undefined control sequence.
\zcolophon …phon\cat * \bigskip \pc \zCopyright
\pc \zLicense \pc \zImageC…
\postptxfile …l}\csname bookend-final\endcsname
\par \fi \ifd@nesw@p \else…
l.523 \ptxfile{631JNLdm-Default.SFM}

This might be related to a USFM marker error (using an unsupported marker).
Try running ‘Basic Checks’ in Paratext to validate markers.
There might be a marker issue in the Extended Study Notes
PTXprint Version 2.3.20
Apparently the problem is an undefined control sequence? What does that mean?
In attempting to track down the problem I did the following tests:
I tried creating a PDF of another Bible book in the same project. Same error message.
I tried a single chapter. Same error message.
I tried creating a PDF of a completely untranslated chapter of another book in the same project, containing only \c and \p codes. Same error message.
I tried a chapter of a different project. PDF created.
I tried copying a chapter of 1 John from my main project into the same 1 John chapter of our Bible app project (which needs to be redone anyway to include newly translated books). PDF created.

Can anyone tell me what might be the problem and how I might correct it? Thank you.

Hi Kirk,

Sorry to hear that this hasn’t been working as expected. There’s obviously something strange tripping it up in the “Colophon”, possibly the \zimagecopyrights or perhaps the \zlicense text. I’m not sure, and can only tell you for sure if you send in a ZIP archive (see the button on the Help tab to do this) to the ptxprint_support address.

However, can I recommend turning OFF the “Colophon at End of Publication” setting, as shown here, to see if that helps you produce scripture normally again.

Thanks. Unchecking Colophon cleared the issue. Or at least the symptom. I guess the underlying issue remains. I’ll send the zip archive.

Looking at the error message, and Mark’s screenshot, I wonder if you might have accidentally turned a \zcopyright (Mark’s screenshot) into \zCopyright (the error message). Alternatively there’s a programming bug for the default value.

Since TeX is case-sensitive, defining \zcopyright (which ptxprint does) and then trying to use \zCopyright will result in the error message you got. Fixing the typo should get you a working colophon