Spot of Tea Bug

After the introduction to the challenge you are asked to place a mushroom growth. Then harvest from bushes to collect teacups. No problem, easy enough until you are lastly instructed to upgrade the mushroom growth to lvl 2. This is not possible. Even after wasting gems to speed up the building's timer, there's no upgrade option. Frustrating.

If you force close your game and try again. I believe something was tweaked earlier by the team, so this should be resolved.... please let us know if not.