Composite key is invalid (KeePass2Android Offline)

Oct 6, 2015 at 5:21 AM
Windows 10 (KeePass 2)
Android 5.1.1 (KeePass2Android Offline 0.9.8b)

From KeePass 2, I export a KeePass 2 DB to a .kdbx file on my PC.
I copy that exported file to my Samsung Galaxy Note 5.
I exit KeePass on my PC.
Still on the PC, I double-click on the .kdbx file now resident on the phone.
KeePass (or Windows) on the PC copies the file into my user directory (deep under AppData), KeePass challenges for a password, and after I enter the password, opens the DB. This is working as expected.

On the phone, I open KeePass2Android Offline, touch the folder in the menu, touch "Open File", touch either "System file picker" or "Get from third-party app", touch the options icon on the top left, touch "Device storage", navigate to the copied file (on the phone) and touch it.

Back at the password challenge, I turn on showing the password, and type it in.
I click on OK. A message box pops up. I think it says "...Loading database", then it closes before I can read it properly, and then KeePass2Android tells me "An error occured. The composite key is invalid."

With KeePass on the PC, I am using password only authentication.
With KeePass2Android Offline, I am using password only authentication.

On the PC my region is Canada, my Windows display language is English (Canada), and my keyboard layout is US.

On the phone, my language is English, my default keyboard is Samsung keyboard. Languages and input also shows the following two keyboards: Keepass2Android Offline, and KP2AKeyboard.

What am I doing wrong?