... I do still have my Sibelius 7 discs I originally started with, should I try to reinstall the sounds from that?
Login to your my.avid.com
account and download the Sibelius Ultimate Sounds
library (most likely just the most recent version of Sib 7 Sounds, I'm downloading now myself).
Yeah I never use that Finder view so I didn't even think of it. That would have been way easier, haha. The second screen cap is what's in the Sibelius Sounds folder. It's what makes me think I still should have the sounds installed because that was left over from Sibelius 7. All the items in the Brass, Guitar, etc. folders are ".patch" files.
What all have you installed outside their normal default locations?
Since it seems you can't recall exactly how you did things initially, it may be a good idea to uninstall everything Sib 19 related and start over. It may not hurt to see about removing all Sib 7.x bits too.
Next screen cap is the full mixer view.
Mixer looks good. (I was looking to see what Sib was wanting to load.)
When I just open Kontakt and load any VDL instrument, I can get playback by clicking a blue key. And when I run the template, add my own instruments, and then manually load that instrument into Kontakt opened from the playback configuration menu, it won't attempt to play but I do get the error message from the last screen cap when I click on a note I've entered.
You should not be loading any patches manually into Kontakt, Sibelius via the Template handles all that for you (once it's all setup correctly of course).
Since you're getting error messages from Kontakt, you may also want to consider uninstalling everything VDL/Kontakt related and starting over with that too. Think "clean slate".
If you go the "do over" route, be sure to do the appropriate backups, and the license key handling (since you're not moving to a different machine, you may not need to deactivate keys). Or, continue to try and fix what's there now.
Let me know.