Sometimes Citrix will think the Chrome Browser is not secure and will not allow access to the Username/Password window. Often times this is caused to a partially updated version of Chrome being used. Typically switching to a different browser will still allow access to the Design Manager program.
To correct, click the lock next to login.designmanager.com and select Site Settings.
Then click Clear Data and Reset Permissions.
Restart the computer. Once the computer starts up again, the login.designmanager.com page should allow you to log in.