Problem editing HTML code

Hello,
I hope someone can help me. I have bought the BonAppetit plugin but i have a problem. I can not acces to the html option of the editor of the posts. The option is disabled. I have disabled all the plugins but the option still does not work. Could it be because it's been installed the new version of wordpress (3.6.1)?

Could someone help me to solve this problem? It is really important and i am in hurry!

Thank you very much!

Antonio

Hi!
Please, try to use these instructions http://smthemes.com/support/topic/wordpress35fixes/.