Symptoms
I created a regular custom list in SP 2013. Then, when I attempt to create a K2 app for it using SmartObjects + Forms, the following error is displayed: "Thread 1: Field or property "MobileDisplayFormURL" does not exist." After clicking "Ok", it returns to the K2 Create application screen (the app is not created).
Diagnoses
The issue is related to the CU and Update that the SharePoint 2013 server is currently on.
Resolution
Upgrading to the latest SharePoint 2013 CU resolves the issue:
CU = KB3127933