It might need the Microsoft Visual C++ Redistributable for Visual Studio 2015, 2017 and 2019:
From your file dates, your portable install of Opus is also a year old, although that probably won't matter for this particular thing (since the DLL is about the same age).
Weird, I have the same issue with not showing up in prefs (12.20)
(Not portable version)
EDIT: Somehow it works now, despite rebooting and installing VC-Redist before
It shows up in my prefs, but doubleclicking an ADF file doesn't work. Dopus then just reopens the folder I was already looking at.
Maybe it's trying to open the ADF file in the lister, notices it's not working, and then refreshes the lister back to when I doubleclicked. I don't know.
any update on this as for me it crashes every time
would love dopus team to show some love to amiga users and have this out the box if it was not for dopus 4 i would not be on dopus 12
We are happy to help plugin authors who have questions, but we have no interest in taking over this project or writing our own ADF plugin, sorry. Our time is already full with other work.
