On Google Chrome, the first time a user clicks the KO button to go to the CloudKO Viewer, Chrome's pop-up blocker prevents CloudKO's viewer from opening. When a pop-up has been prevented from opening, a blocked pop-up icon  will appear in the right hand side of the address bar. 

To allow the CloudKO Viewer to open follow these steps:

1.  Click the blocked pop-up icon  in the right hand side of the address bar

2. A window will appear. In it click Always allow pop-ups from https://app.cloudko.com and click the Done button

3. Now, attempt to open the viewer again. A new tab should open with the viewer.