Well, never mind. It turns out my file renaming format on the import was wonky. :-P One nice thing I discovered is that if you run digiKam from the GNU debugger, it provides all sorts of useful information.
J I tracked the “failed to download” to umscamera.cpp on the rename of the temp file to the target name, and that’s when I found the error.
From: Tom Cunningham
Sent: Monday, February 13, 2017 10:53 PM
To: [hidden email]
Subject: RE: digiKam 5.4.0 on Windows 10 failed to download
Still having this issue. Nothing worked this time, not even “Download New”. Stymied; still using Picasa to import.
From: Tom Cunningham [[hidden email]]
Sent: Saturday, February 4, 2017 11:13 AM
To: [hidden email]
Subject: digiKam 5.4.0 on Windows 10 failed to download
I am unable to download from a Sony RX100II or direct from SD card using either “Import->Download All” or “Import->Download Selected”. For every file I select, I get “failed to download.” “Import->Download New” seems to work, but it doesn’t
perform any of the custom file renaming I have specified.