My Lands: Black Gem Hunting

I think that may have been the problem. Thanks.

I have a quest to upgrade three production buildings and three cottages to level 2. I have the ability to build and builders available. I click on the building and then the green arrow. However, the upgrade button does not glow so that I can push it.

Does anyone know why?

I just began the game today and am hooked. I would like a mentor so I can grow quickly. Thanks.