Scenario:
You have Market level 21 to 24 in the building queue. Now your farm is too small to also build Market level 25.
However, the main building does show the upgrade button, until the 24th level has been built, then it shows "farm is too small".
Scenario: You have Market level 21 to 24 in the building queue. Now your farm is too small to also build Market level 25. However, the main building does show the upgrade button, until the 24th level has been built, then it shows "farm is too small".