Symptoms

Error: Multiple authentication attempts detected
Details:
Detected an instance where Relying Trust is not configured properly, and requesting tokens repeatedly. Please ensure that the link to the K2 server is added to the browser's trusted sites.
 

Diagnoses

Add K2 designer site to trusted sites in IE
Grant IIS_IUSRS group Modify rights to the WindowsTemp directory
 

Resolution

Granting IIS_IUSRS group Modify rights to the WindowsTemp directory should help resolve the issue.