FYI I noticed one of the flights in the RTMM flight plans zip was not visible to P3D for loading. After some troubleshooting, I determined a '&' in the DestinationName field of the PLN file was the culprit. It does not cause a problem in the filename, but rather within this specific field of the file contents.
Flight = Owikeno Casino & Resort (OCAR) from Owikeno N Strip (PF39) -- aka MFC0445A
Change
<DestinationName>Owikeno Casino & Resort</DestinationName>
to
<DestinationName>Owikeno Casino Resort</DestinationName>
Brian