Problem
Runtime Error
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.Details: To enable the details of this specific error message to be viewable on remote machines, please create a customErrors tag within a 'web.config' configuration file located in the root directory of the current web application. This customErrors tag should then have its 'mode' attribute set to 'Off'.Notes: The current error page you are seeing can be replaced by a custom error page by modifying the 'defaultRedirect' attribute of the application's customErrors configuration tag to point to a custom error page URL.
Solution
Try to perform an IISRESET first to see if it resolves the issue.
If it does not, then you will need to turn off customErrors to unmask the actual error message:1. Make a backup of the K2 Designer web.config found in {K2 Installation Folder}\K2 Smartforms Designer\2. Open this on any text editor and look for the following line:customErrors mode='RemoteOnly' defaultRedirect='Error.aspx' redirectMode='ResponseRewrite' 3. Change mode to 'Off' so it becomes like this:customErrors mode='Off' defaultRedirect='Error.aspx' redirectMode='ResponseRewrite' 4. Save the web.config