Symptoms
The remote server returned an error: (404) Not Found.
Diagnoses
After the initial form submission when I open the Approval form from k2 workspace I am getting an error "Worklist item could not be loaded". Previously I was able to modify the URL with SP List ID and load all the data's but now I am not even able to get that working. Instead getting an error"The remote server returned an error: (404) Not Found".
Resolution
404 was due to SmartObject/SharePoint having over 100 columns.
https://technet.microsoft.com/en-us/library/cc262787.aspx?f=255andMSPPError=-2147217396