This looks as if something went wrong with the Core Data datastore. Unfortunately, as you have already deleted and reinstalled DEVONthink To Go the log files are also gone (they are deleted by iOS when you deinstalled the app). Let’s keep the fingers crossed that it won’t happen again.
You can send us the log by using ? > Contact Us from the database screen or by opening Files > On My Device > DEVONthink. There’s a file called Console.log that has way more information that the user-facing log inside the app.
The same has happened to me; one of my databases - which is synced via Bonjour from my Mac to my iOS devices - has 0 files on both my iPad and my iPhone (and 651 items on the Mac). As with the OP, opening the database on the iOS devices only shows “Record List” rather than any other content. Eric, I’ve mailed you the console and sync logs from the iPad.
There was nothing in the logs which was of any help.
The solution in my case was to turn off sync for the affected database, delete the database from DTTG on the iOS device by swiping left on the database name, confirming that I reeeeeally want to do that, then once it had gone simply turning back on sync. The database was then synced back from the Mac. In my case, however, I’m sure there was no data added to the database from DTTG, so deleting the database was risk free. If I had added data which had not synced to the Mac, things would be different.
This has just happened again on both my iPad and iPhone. The affected database is fine on both Macs, as are other databases on iPhone and iPad.
I have sent the logs from the iPad in on ticket #366216.
Last time I recovered by uninstalling DTTG completely and starting afresh. This lost all the logs of course. Blanc’s easier method would not lose the logs, and I have done what he did on my iPhone, but not at this point on my iPad.
Note that Repair and Verify on the affected database on iPhone and iPad says it is OK.
A change since my OP on this problem, is that I am now only using CloudKit sync, having turned off Bonjour (which was source of many messages. CloudKit alone is the best syncing experience I haver had with DT)
What a strange issue, especially as a reboot seems to fix it. Could you send us the Console.log that you find in Files.app > On My Device > DEVONthink?
Just jumping on here to share that I am experiencing the same issue as the OP with DTTG on my iPad. The items are still available and visible in the relevant database on Mac and iPhone but disappeared on the iPad. Only one out of three databases are affected.
Since I have the databases available on other devices and backed up on Dropbox, I believe it is relatively low-risk to delete the DB from DTTG on the iPad (after turning sync off) and then turn sync on again after.
Despite the perceived lower risk, I am somewhat anxious as this particular DB is my most valuable one by far and I will be ruined if I lose it.
So, just that I understand correctly: it’s not temporarily and cured by, e.g., killing and relaunching the app. It’s persistent and was, for some, cured by a device restart (means: it was something in iOS that caused it or a rebook wouldn’t have had any effect). And for some a reboot didn’t help.