Symptoms
SmarForms viewer is missing.
Diagnoses
K2 webparts and components are missing.
Resolution
1. After installing K2 SmartForms on the K2 server, you also need to run K2 SmartForms installation files in the 'K2 SmartForms for Sharepoint' components on the WFEs and the server hosting Central Administration.
2. If you have done step 1 from above, you need to rerun the 'K2 for Sharepoint configuration wizard' while logged on the Central Administration Server to deploy the SmartForms solution.
3. Please proceed with an 'update all', of the upgrade all of the features and then perform a reactivation of the K2 features, and K2 configuration settings to the site collection where you are attempting to see the K2 Smartforms Webpart.