The chord diagram for Dm7 at the start of a flow is missing the barré indication. It shows up in the diagram of the stave however:
Everything is fine with the F major chord diagram or indeed every other diagram I came across, just that Dm7 does not work as intended.
Do you find that this problem occurs in a newly-created project, or does it appear to be isolated to a particular project file?
The problem occurs in all files that use this chord diagram, also newly-created empty projects.
I can’t say for sure it is only this diagram, but so far, it’s the only one I came across that does not word as intended.
Select the chord diagram then right-click it and choose Chord Diagrams > Show All Variants of Chord Diagram from the drop-down menu. You can choose the one you want from those displayed.
My apologies. As a relative newcomer to Dorico (who has not needed to use chord symbols or diagrams yet), I was not aware that it was possible to place chord diagrams at the start of a flow, before the actual music. I have just tried what you described (now that I know what to do) and have replicated your experience. I’m sure Daniel Spreadbury will be investigating.
When I selected the Dm7 chord diagram above the staff and used alt/opt-Q to cycle through the various possibilities, the diagram at the start is indeed missing the barré indication.
No need to apologize. You will find Dorico is fantastic for all things guitar related. Go and watch the videos on the Dorico Youtube channel https://www.youtube.com/channel/UCIOwP19omIVDSUq2rTGgHKw, you will learn a lot. Have fun!
Should be easy to correct that small bit of code, shouldn’t it? 
