I have the same problem. I tried to disable all other mods to test if it was a combination of them making it happen, but no. With Colonize Unlimited as the only mod, it's still not triggering anything.

It doesn't change the planets habitability score on the Planet Summary, or allow me to resettle humans on the barren planet (or even on the tile).

Interestingly, I have the same issue with the Frontier Clinic, it doesn't do anything either. I'm now going to try another game in vanilla just to test if it is Paradox-programming that might have changed the mechanic.

As far as I can tell it isn't this mod.

Without mods a worked Frontier Clinic doesn't change habitability on an Arctic worlds for my Continental humans. It might be that the effect have been removed.

So, if I remember correctly, this mod give barren a +20 habability modifier.
So, one solution to settle on the barren planets could be picking the Extremely Adaptive Trait. It could be roleplayed as the people already knowing how to use biospheres as they leave Earth.

It would still mean that the folks wouldn't quite be happy about it with happiness capped at 40%.

As for the buildings not working, I'm obviously no modder, but this problem could be solved by making the +40 (or +5) for the buildings trigger via technology instead. The Tech for Frontier Clinic could simply add another +5 similar to the techs we already have doing that (which work in vanilla and this mod).
And the +40 could come in tiered tech with +5 each indicating new developments in Biosphere building. It wouldn't cost as much as the actual building in upkeep, but it would mean a serious dedication to the idea of colonization.

I think if you try to change habitability of 0 by 40% it's still 0. You'll probably have to up the habitability in some other form first.

I'll have a look to see what's happening.

I have created a workaround for the buildings that effect habitability scores and I made an add-on mod for Colonize Unlimited that will allow the Enclosed Biosphere to work as intended.
Habitability Fix - Colonize Unlimited Patch

Hmmm... Did it change so you don't specify the habitability change on the building only?

Originally posted by Dosaki:

Hmmm... Did it change so you don't specify the habitability change on the building only?

Currently, I think the feature is just broken for buildings. I have not found a way to fix it by editing the entry in the buildings.We may be at the mercy of Paradox Devs. I hope they fix it soon, but it seems to not affect vanilla gameplay that much so I'm not sure they will fix it quickly.

It acts as a pop modifier not a planetary one...