Why is my FM12 no longer generating context-sensitive help?

I have a well-established book file that was already successfully used to publish context-sensitive help for our previous release, and now it is no longer generating an .h file, or apparently reading the one I include.

Facts:

* my FM documents contain TopicAlias markers

* in the same directory as my FM book file there is a .h file called <my_book_file_name>.h

* this .h file contains definitions of mapIDs with unique numbers

* when I generate HTML5 output (even if I do it to a "clean" folder, so not overwriting old output), no .h file is generated.

* the csh.js file in my HTML5 output is empty

* if I look into the source of my individual html files, there is no CSH marker in there

what am I missing?

please help!