I created a new master page that looks like this:
I applied it to a flow. Everything seems to work except the flowtitle, which is blank. Yes, I do have a title for the flow. flowcomposer and flowcopyright appear just fine. I just tried adding flowlyricist and that worked as well.
In Layout Options, show flow headings is set to “For all flows”.
I may be screwing things up by putting the flowtitle into a page template rather than a flow template, but every other flow token seems to work. I can replace flowtitle with flowcomposer and the composer’s name appears where the title should.
There must be some option somewhere that I don’t know about. Admittedly, I’m new to Dorico, so this seems the most likely source of the problem.