Hello, I’m still using DT Pro Office 2.11.3, syncing via iCloud. I just bought a new MacBook Pro, and after using the migration assistant, opened DT. Everything in my database appears, but the log is now showing two errors:
The file “master.plist” couldn’t be opened. NSCocoaErrorDomain 256
The file “DEVONthink” couldn’t be opened. NSCocoaErrorDomain 256
These errors will repeat if I leave the app open. Any help would be greatly appreciated!
I figured it out, so in case anyone else in the future has the same problem, the solution was to go to System Preferences > Security & Privacy and enable DEVONthink in the “Full Disk Access” section.
Thanks for the follow-up. 
FWIW, I am having this same problem on iOS (DT to go)
For some reason my sync stopped on Nov 21 and now I get similar errors like:
The file “master.plist” couldn’t be opened. NSCocoaErrorDomain 256
and
The file “DEVONthink” couldn’t be opened
Any ideas how to resolve on iOS aside from deleting app and starting over?
Which version of DEVONthink To Go and of iOS do you use?
Im now getting the same problem. DEVONthink to go V 2.7.6 (16388) iOS version
13.2.3
Does updating to iOS 13.3 fix this?
Good evening,
while the errors mentioned above occurred for me in a completely different context, the solution still fixed my issue. Just wanted to point that out for anyone searching the forum by this error code.
Thanks for the follow-up and assuming you’re running DEVONthink 4.x, check out the Getting Started > First and Last Steps section of the built-in Help and manual for information on macOS’ Privacy & Security settings relative to DEVONthink.
Thanks, I’m going to have a look at that too.
You’re welcome 