Looks like DroidFS cannot access those folders (volumes).
Make sure to give Files permission to DroidFS.
If you are using GOS and enabled StorageScopes then give access to those specific folders (volumes) to DroidFS by adding those folders to StorageScopes.
To the problem where you get error “Open failed” I recommend you to instead of using any frontend, directly open (mount) those encrypted and synced folders via command line and use them with any file manager.
Edit 1 -
3-4 years ago I moved from Cryptomator to gocryptfs and now cryfs (after DroidFS added support for cryfs).
Reasons for moving from Cryptomator -
- You need to pay again to unlock Dark theme on PC app after once paying for Android app.
They call this “donation”.
(I don’t know if things changed now.) - Second issue for me was personal, the way I use my system, gocryptfs made much more sense.
Edit 2 -
Table comparing Cryptomator, gocryptfs, cryfs and many other projects