Summer Event: Using upgrade kits

Got a upgrade kit but cannot upgrade it! Why?

Please check in your inventory if it's a Crow's Nest or an upgrade kit. You cannot build a Crow's Nest with an upgrade kit, and in order to upgrade your Crow's Nestyou will need an upgrade kit:

The Crow's Nest - Level 1The Crow's Nest Upgrade Kit

The same applies to The Ship, and other upgradable buildings.