Symptoms

When trying to create a new workflow, the Silverlight spinner spins for a while, and then the content pane of the K2 Designer just goes blank.
 

Diagnoses

As a test, we tried to "download" various different files from the server that hosted the K2 SmartForms Designer component. We created an "html" file in the same directory where the "XAP" files for the K2 Designer resides.

Using IE on the client machines.

1.) Hit the "K2 Designer" in order to authenticate.
2.) After successful authentication, we would try to "download" the HTML file, by "browsing" to the following URL: "https:///URL]/Designer/Workflow/ClientBin/test.htm" and we were able to see the HTML file.
- We tried grabbing a "bin" file from the same directory, and it worked.
- We tried to hit the URL to grab the XAP file from the server
http:///URL]/Designer/Workflow/ClientBin/blank.xap.
This did not work.
- We changed the extension of a "XAP" file to "Bin", and that worked.
- Then we changed the extension of "BIN" file to "XAP", and that failed.

This all seems to point that there is some form of content filtering that is preventing the browser from downloading the XAP file it needs, to create a new workflow. (All other files seems to download just fine.)

 

Resolution

Issue was with the Firewall rule. It didn?t allow Silverlight XAP files through.
The firewall rules and the time-zones of their servers also played a part here.

Some servers were in different time-zones than the client machines. "Business hours" on the "firewall" configuration, was why this worked in one environment, but not the other. (Even after unblocking XAP files form the block list.)