I have set dopus as the default image viewer for every type of image, and have even installed the Directory Opus Helper Application (the .reg file posted elsewhere on this site), but every time I run ACDsee for advanced imaged editing, I lose the defaults for dopus and have to reset them again in Windows 10.
Very frustrating. Please help.
If it works until you launch ACDSee then ACDSee must be modifying the file types to take them over for itself each time you run it.
How to stop ACDSee from doing that is a question to ask the people who make ACDSee.
Yes, I forgot to mention that - I thought the same and probably you are right, except that I have disabled all file associations within ACDsee, so I thought perhaps there was something going wrong with dopus. I guess not, right?
It is unlikely that it is Opus if the change happens when you run ACDSee, if that is what's happening.
okee dokee
Hi. Back again.
I have uninstalled ACDsee just to see what kind of result I'll get with this. I'm still having problems.
When trying to open an image file (let's say JPG) which is attached to an email in Outlook 2016 desktop, the file does not open and no action takes place at all. This is true even when Directory Opus Helper Application is properly set as the default for all photos in Windows 10. If I take the JPG out of Outlook and put it in my file system, then double-click, it opens. However, if I right-click > open with on that file, and choose D8Viewer and set as default instead of the Helper Application, then I can double-click in Outlook. However... Windows keeps losing that setting and there seems to be no way to set D8Viewer as the default for all images file types.
I wonder if I'm explaining this properly.
It sounds like something on your system is messing up the file types. Maybe it isn't ACDsee but something else.
Or there's some other complication, like running different programs under different user accounts, which can get confusing.
In Opus, you can use Settings > File Types, and then click the File menu and select Diagnostic, to save a diagnostic output about a particular file extension. Looking at that may provide a clue about what is messing things up.
If you do it before and after the problem occurs, and save/rename the output each time, then we can compare things when they work vs when they stop working, which may indicate what is changing, and in turn point to what is likely to be changing it.
My guess is something is trying to "protect" your file type associations and reset them, and it won't be Opus that's doing that if so.
Thanks. I've produced the report and will again as you suggest when it goes bad. I'll get back to you.
Hello. It's been a long time since I initiated this ticket but I'm back with a similar issue.
I have recently got a new laptop and since installing everything, I cannot open JPG files from within Outlook, though there is no problem from the file system - the file association is correct, it seems.
Please help.
Todd
Opus isn't really involved with what Outlook does. Or do you mean you're trying to open the Opus viewer from Outlook?
Yes, the opus viewer from withing outlook. 
Open With > Always use this app... should be all you need, unless something else is messing with your file types or Outlook is not opening the file properly.
Note that you need to do that for each file type/extension you want to open.
Since it was working for a while and then stopped working, my guess is some other software on your PC is messing with the file types.
The diagnostic I mentioned in the Mar 22, 2017 post above may be worth doing in that case.
I have now forced the file associations to use D8Viewer.exe instead of the Dopus Helper Application, which has solved the problem. I believe the problem is with the Dopus Helper App and if you are interested in investigating, I'm happy to put in that time with you.
