I believe I completed the Define Sharing Rules challenge.  When I press the Check Challenge button, the following error is displayed:

Challenge Not yet complete... here's what's wrong: 
An object with the API name Project__c does not exist or does not contain the Priority__c picklist field.

I did create the Project object.  When view the Project object it indicates that the API Name is Project_c.  It has a custom field called Priority and the API Name is Priority_c.

What is going on with this challenge?