If you are experiencing an abrupt crash when registering your DEVONthink license in DEVONthink To Go, please do the following: in the database list, click on the sorting symbol (three horizontal lines) and enable unify tags and inboxes. After this has been done you should be able to register DEVONthink To Go. After your license is registered, you can revert back to the old tag setting.
Feedback if this worked for you is greatly appreciated.
Still doesn’t work for me
Did you restart the all after the change? (And before the registration attempt)
Don’t think I restarted between the two steps. Tried repeating the steps from the beginning with a restart in between, still no joy.
Do you have unified inboxes enabled?
No. Tried enabling that too, same result.
Have you tried enabling both at the same time?
Yeah, same outcome.
I get something new this time. Whereas before the app would CRASH after hitting the checkmark to register a mobile seat, after that, now I see a new error message: “Sorry Internal Error.”
The app no longer crashes.
I force closed, no change.
UPDATE: After toggling the unify tags/inboxes a few times and restarting the app, it crashes again!
Version 4.0.1 is on its way into the App Store review.
Sorry, it doesn’t on my iPad. Checked, unchecked, restarted DTG, restarted the iPad, to no avail.
Waiting for 4.0.1
Which has just become available an hour ago.
And it’s working, too! 
Issue solved for me 
Confirmed “seen”, downloaded, and licensed. Thanks.
With 4.0.1 I can now register the license without the app crashing, but now it’s not retaining that I registered the license on iPad/iOS after I leave and then return to the app.
So you log into your customer account and choose your license to register with. You tap the checkmark button and the license is shown as registered in the settings with a yellow checkmark? And it still forgets it after an app relaunch?
Yeah, that’s what’s happening.
Action (…) button > Settings > About > Contact Us.
Yes, I’m seeing same now. When I try to do something the screen about it “free” for a while comes up with a button to the licensing screen, which shows “not licensed” … even though I did the successfully with 4.0.1 yesterday. I’ll send in an “Contact Us” as suggested by @bluefrog to @chezkitch.
Same issue here. Whether you manually kill the app or leave it long enough for iOS to kill it in the background.
The app is also freezing for me, I’ll raise a ticket for this one.
