Symptoms

File attachment control not working in Chrome. For our international users, the file upload doesn't work in IE and Chrome.
 

Diagnoses

Conducted Go To meeting. The control behaves as though it is dead, no reaction on mouse-over and no reaction on clicking.
The issue is in Prod. The control works in QA, both in Chrome and in IE.
Customer upgraded from 4.6.7 to 4.6.11 in January. All other environment details remain the same.
Customer had same issue last month in a different ticket. Resolution was unclear although the customer believed it to be a Kerberos issue.
Customer's International people access the form through a Citrix Portal, the control does not work in either IE (v 11) or in Chrome (V49).
Ticket owner is using a client machine and can get the control to work in IE 11 but not in Chrome. Another user on a different client machine near him has identical issue.
When ticket owner tries the control through the CITRIX portal (in Prod), it does not work in Chrome or IE, which is same problem his international users have.
Customer created a simple test view in Prod with just a file attachment control and experienced the same problem. He PandampD?d the test project and attached to the ticket. The control worked successfully in Support VM with same environment.

 

Resolution

Customer was advised to run this cache control - modifying the URL to match their environment: https://k2.denallix.com/Runtime/Runtime/cachecontrol.ashx?m=clear
This cleared the issue. That cache control reached into the IIS - so something in the IIS had triggered the issue. Since there are lots of things in the IIS that are not K2 related so there is no way from our end to clearly identify what might have happened.