Hi,
I am having the same issue, and it sounds like it might be a version issue like the previous people.
Sibelius: 2018.7
Kontakt 6
VDL 2.5.5
Again, everything seems to be in the right places and loaded, but the sound set does not show the VDL template XML as an option
my Kontakt player in Sibelius shows up as an "AU" type. I know previously it there was a "VSL" option. Does this play a role in my issue?