Try
It is not only missing in the Help menu…
It’s also missing if you try “F1” key for help.
Which on PC will give you a popup saying something similar to -
“Could not find the manual!”
C:\Program Files\Steinberg\Cubase 9\documentation\Operation_Manual.pdf"
to fix it…
create the folder
C:\Program Files\Steinberg\Cubase 9\documentation\
unzip the files from the following documentation download (English) into the documentation folder you created:
http://download.steinberg.net/downloads_software/Cubase_Pro_9_and_Cubase_Artist_9/Cubase_Pro_Artist_9_PDF_documentation_english.zip
F1 will then launch the Op Manual PDF.