Possible Reasons:
 MIME types not set
 Missing project files
 No startup screen set (Secure Viewer)
 ISSymbol.ocx has been blocked from uploading or updating I.E. (Win 8 Security)

Solution:
 Configure the MIME types in IIS
 Republish the project
 Run ThinClientSetup.exe on the target machine to manually load the ISSymbol.ocx, or start I.E. under Run As Administrator to update the plug-in, then restart normally.

Released for: Schneider Electric India