[General] Making Neutral Passive buildings sell upgrades?

[Slaver]

I'm somehow failing to manage upgrades at a creep-building location; they simply don't show up even though I do everything normally.
I placed all my custom (and non-custom) upgrades where they belong in the,
"Techtree - Research Available" box and for some reason, in-game, they're not there. Only units or items seem to show up, but upgrades don't seem to be purchasable from marketplace-type structures and I'm not sure why. I'm certain this isn't typical as I don't remember this being an issue before.

I'm scratching my head trying to figure out why they're not appearing. Any help?

 

[Eye]

Me always assumed by default, - you can not. Never tested much, can't downgrade researches, rarely use 'em now.
Tried this too, does not work.
Similar question here.
Can you downgrade a research on the newer patches? If you are using one. I've seen some new functions somewhere.