Just upgraded from CE12 to CE13. The Help option on the menu bar a) takes you to an Error 404 and b) no longer has the manuals available. Is this right?
What is your preferred PDF reader on your computer? Is it your web browser? I would think that any help files are probably PDFs that will want to open up in a PDF reader. If they’re not then the help files are maybe now online files instead. Are you connected to the internet when you try to open the help files?
I use Elements 13 on Windows 10 but I’m not at home at the moment to check what my system does.
If you open any other PDF files on your computer what happens to them?
You can download documentation from here but you need to set the filters to your version and then click the download icon:
https://www.steinberg.help/search/documents?filters=product_names_smtg~%2522Cubase%2522*version_numbers_smtg~%252213.0%2522&virtual-field=title_only&content-lang=en-US
This is the old (easier for those of us who are intellectually challenged) page.
I can open them up elsewhere in pdf. It was just handy to have them available from the bar.