I had the same problem and I am wondering if it will fix itself when I research atmospheric cleansing or the actual barren planet tech? Definitely a bug.  

I've seen that thread, but my custom race doesn't have the Adaptable trait.  So I think it's a separate issue, but I could be wrong.

Anyway, I went ahead and researched the Barren planet tech and I still can't colonize the planet.  Atmospheric Cleansing isn't available until the Age of Ascension, so it's going to be a good long time before I try to see if getting that allows colonization.

Oi! Oi! I hope it's an easy fix.

I am definitely now seeing this issue with a new race.   Research extreme and get frozen, aquatic, etc. but not barren.  Definitely weird.

What it looks to me is in the tech tree Barren is not researched even though you think it is.

Also running into this issue. Have Extreme Colonization researched along with every mastery spec and it won't let me colonize a barren world.

so looking a little more propagation tech is the first tech of the yor population tech tree so im guessing that having that line in there was a cheap way of giving them the ability to colonize barren, aquatic and frozen planets without having super abilities working yet

as a side that means anyone using the yor tech tree can colonize frozen and aquatic worlds right off the start regardless of having adaptable or not

ive made the changes i suggested and am testing it now although i had to leave propagation tech in as a possible requirement for the three planet types since i think the yor tech tree doesnt actually have an extreme planet colonization tech ability

Any more info on puzzling this out?

so after a bunch of testing i cannot get this to work properly

i can get the planets to be colonizable eithar one way or the other if you have the tech or have the ability but this requires 2 different setups 

or i can set it up so that you can only colonize if you have both the tech and the ability

maybe someone with better skills then I have can fix it

some thoughts 

having the ability grant the techs should work but i cant figure out how to grant techs (and i dont know how this would effect tech progression)

having the tech grant the ability would work but i cant figure out how ( this would be annoying as you would have to edit all tech trees)

having each of the tags under <ColonizationPrerequ> be treated as an OR operation rather then an AND operation would work (similar to how the <option> tags work but putting them outside the <tech> and <stat> tags causes an error

Observations from testing:

-Most races can't colonize Barren worlds with any level of technology.

-Races with "Adaptable" and any tech tech tree other than Yor can only colonize Barren worlds until they research Extreme Colonization.

-Races with "Adaptable" and the Yor tech tree (including the Yor) can colonize all three.

-Races with the Yor tech tree but not "Adaptable" can colonize as though they have Extreme Worlds technology!  They are able to colonize Frozen and Aquatic without choosing adaptable but they cannot colonize Barren worlds.  They get most of the benefits of Adaptable but get 2 other abilities to go along with it.

Thanks for reporting this issue! I've created an internal bug report and forwarded it to the development team for their review.

For anyone else experiencing this issue with or without a custom race, please create a ticket using our support system and provide the data requested in the article below. This will ensure the dev team has all the data they need:

https://esupport.stardock.com/index.php?/default_import/Knowledgebase/Article/View/496/161/general-galactic-civilizations-iii-troubleshooting#support