Commented Unassigned: Cannot open .kdbx from SpiderOak [78]

When I try to open my database from outside Keepass2Android (specifically via the SpiderOak client), my phone will not give me the option to open it in Keepass2Android. I'm guessing this is because it's not registered as a handler for .kdbx files, but maybe I'm missing something obvious.

Samsung Galaxy Nexus (toroplus hardware variant), running CyanogenMod 10.1.3 RC2.
Comments: I used to open KeePass2Android from Google Drive by just clicking on the file. Something must have changed recently since that does not work any more. I have a Samsung with Android 5.1.1. If I use the native file manager or Astro File Manager, I can click on the Google Drive kdbx file and open it with KeePass2Android. FYI, both file managers download a copy of the kdbx file and use the copy. The MIME-Type field of the original file shows application/octet-stream while the copy shows a null field. Does this help? Thanks