Having trouble activating Terraforming Engineers

[vigorousRoll]

It's round 8 and we've just entered phase III, the Settle phase. I have Terraforming Engineers in my tableau along with novelty world Gem World, which costs 2 to place. I have novelty world Galactic Studios in my hand, which costs 5 to place. The second portion of TE's III power description reads, "May replace (at no cost) one non-military world with a 0-3 higher cost non-military world of the same type to gain one unit of Prestige (this is not a Settle action and cannot be combined with other Settle powers)." Galactic Studios and Gem World are both non-military.

I called Settle and plan on placing another world from my hand but I thought I would get this special situation taken care of first. So I clicked on Terraforming Engineers in my tableau and nothing happened. I clicked on Gem World from my tableau and nothing happened. I then clicked on Galactic Studios from my hand and the software sent it from my hand to my tableau with the message "You must pay 4 cards for this world" (the other portion of TE's III power grants a 1-card discount for Settling). I don't have 4 other cards in my hand, I only have 2. So while GalacticS was hovering there in my tableau, I clicked on Terraforming Engineers and nothing happened. I then clicked on Gem World and nothing happened.

I can't figure out any other path to try to make this exchange become a reality. Do I have to wait until my normal Settle is completed before the software will let me exercise this special ability of Terraforming Engineers ?

[vigorousRoll]

Ok, I went ahead and bit the bullet and executed a double Settle with the help of Improved Logistics and my opponent had already made his Settle choice. Then a message appeared up in the action window that read, "Terraforming Engineers: You may replace a world." It was accompanied with a blue box that read "I choose not to". I first clicked on the world from my tableau that I wished to replace and then clicked on the world in my hand that I wished to replace it with and the software executed the exchange.

So for anyone like me who is new to these expansions and is curious about how this subsection of Terraforming Engineers' "dogma" works, you'll be prompted about TE after all the normal Settles are executed.

[Gerb81]

Just run against the same "issue". Tried for a half hour to activate it.
Should be more clear that it is after the normal action