Symptoms

I have created a dropdown list on the form that uses a custom list in the SharePoint server. The dropdown gets its data from the sql server smartobject. When I run it within the K2 designer, I can see the list working perfectly. However when I use it on the SharePoint site, the list is not populated. I have attached both images for your consideration.
 

Diagnoses

- Issue with Authentication Mode being used for the SQL Service Instance.
- K2 service account permission on the SQL database.
 

Resolution

Try switching the Authentication Mode for the SQL Service Instance to 'ServiceAccount' and grant the K2 Service Account needed permission in the backend SQL database.