Well your guess is as good as mine, Guitarhacker.

When I asked for a specific reason why two of my tracks were approved for monetization and six were not, this is the exact reply I received from LANDR's Rescue Squad:

"To me, it sounds like the tracks that used a keyboard were being questioned as something that you may have used from a DAW, which is why some of your tracks were approved and others weren't.
I've gone ahead and overridden the decisions regarding monetization and have made your tracks eligible.
Keep in mind though, that this won't guarantee monetization on Youtube! They are the ones who will make the ultimate decision".

Make from that what you will.
If you want to check out the eight songs to see if you can identify what the reason could be, they are all streaming on Spotify.
The two that were approved were 'I Want You' and 'Light in The Dark'.

https://linktr.ee/andyshearer