Hello, I’ve seen other people upgrading their buildings so I don’t think it is broken. When you upgrade a coop you have to upgrade a pre-existing building. I’m assuming that you already have a normal coop on your farm, that is not under construction.

In the building menu the second tab on the right (the middle one) takes you to the upgrades section of the UI. Presumably, you are going from a normal coop to an adequate coop. You should just have to select it and then when it takes you to your farm click on the coop you want to upgrade. Once you do you should see a construction sign appear outside of the coop signalling that it is being worked on.

If you still have issues let me know, but I’d be surprised if it was broken.