This error typically is caused by the application looking for an instance of SQL Server that does not exist or is not running. Confirm that the server name in the .ini file for the application is the correct server.
The file is found here: 'C:\Program Files (x86)\Esha Research\FoodProSQL\FoodProSQL.ini'. If Windows 7 or Vista, this can also be found in 'C:\Users\[UserProfile]\AppData\Local\VirtualStore\Program Files (x86)\Esha Research\FoodProSQL\FoodProSQL.ini'.
If the server name is correct, confirm that the SQL Server instance is running. You can check either SQL Server Configuration Manager or Services.msc.