Do you have enough nutrition to grow the Zooid? If you do, could you provide a screenshot of how the game looks when you can't select it? Also, you can try using number key 4 on keyboard to select Consumption Zooid group to grow?
Thanks, we'll think of something to prevent this overlap!
As a workaround you can either change UI scaling in Options menu or you can use "4" key on keyboard to select and cycle through Consumption Zooid category
