You have used up your last wheat. The game will prompt you when you attempt to use your last wheat but I think you missed that. Are you able to open your shop? Thats the only way you can buy besides using gems.
I noticed you have set up 2 threads of this topic. I have deleted your other thread since its a duplicate.
Sorry I have deleted before you added the last comment.
You could buy from newspaper or side shop after you have repaired your shop or use a gem for a wheat if you do not wish to wait.
Alternatively you may want to try to send an email to support@storm8.com and see if support can give you a wheat. Thanks.
Come to my shop, I put some wheat up for sale.
Go to Social, enter her id under Invite tab.
You can visit her farm by clicking visit button next to her farm name.