Unable to open underlying documents

I am using “download on demand”. On several occasions, on both my iPad and iPhone, I have been unable to open any document (whether RTF, PDF, or simple text) in one database (though the actually directory structure and file names display appropriately) despite hitting the “Download” button multiple times. However, I am able to open up all documents in another database. It has happened in two distinct databases (out of a total of 5 databases that I am using)

If I delete the database on my iPhone or iPad and then re-sync, this seems to solve the problem. I cannot state what causes this issue to occur, but it has happened several times over the weekend while testing DTTG.

I have attached a screenshot to show that the underlying document does not open.

If you have indexed files and chosen to not include indexed contents when you Sync to a Sync location, a device you Sync with this location will have no contents to download.

That was not the issue. I was syncing the database content. However, the issue does seem to be resolved by upgrading to DevonThink 2.9.1.

Negative the issue is still occurring.

Could you please post screenshots of the settings of the sync location on OS X and iOS? Does a verification of the sync store report any issues?