Calibre MOBI format not seen in PC Kindle Library
I've been using Calibre for a long time, mostly to download and convert news feeds into MOBI format for reading on the Kindle for PC software.
All was good until at some point after version 0.8.20, the MOBI files created by Calibre no longer show up in the Kindle library (I'm using the latest PC Kindle version 188.8.131.52179).
Something changed in the MOBI output, but I haven't been able to figure out what. Accordingly, I'm stuck at 0.8.20.