Ummmm… if you can not donate an order (the button is gray), please check the following:
You have this dish in your storage. You need to have the exact dish in your storage that the player is asking for, this includes upgraded dishes.
You have used the + and - buttons and have donated an order
The Donate button will turn green if you have the correct dish in your storage and have donated an order correctly.
Do NOT worry…If you do not have the dish the player is asking for and if they are not your restaurant buddy already you can now follow them. This will place the player into your social bar and you will be able to go back to the restaurant and help them at another time if you wish.