Out of the blue when I download from Chrome, the file doesn't appear in DO. I can see it in File Explorer. DO has been working perfectly for well over a decade, now suddenly, this happens. Even after a restart, the previously downloaded file doesn't appear in DO!
Does the status bar indicate any files are being hidden by filters?
Are you definitely.looking at the same folder in both programs? (Windows now has multiple folders with the same names but which aren't the same. e.g. There are several "Desktop" and "Documents" virtual folders and libraries which show different combinations of the real underlying directories.)
If you're using Windows Defender, try excluding dopus.eze from it's protected folder / privacy guard functionality, as that causes all sorts of strange issues.
To say that I'm a dill would be being kind 
. I explained the problem incorrectly: The save dialog (which I understand is DO as DO has replaced File Explorer completely) for saving the pdf can't see the new folder I created to receive the download.
It continues. It's not DO, it's me ! ! I was looking in a backup directory - identical names and structure, but different disk. I created the new folders there. No wonder the save dialog couldn't see the folders where I thought I put them, - they weren't there. Tail between my legs, I'm retiring. Sorry to have caused you any trouble.
Keep up the great work with your fabulous product.
The Save dialog has no connection to Opus.