One thing that can cause is due to blocking of third-party cookies and data. Here are some workaround steps to help resolve this issue:
1) Google Chrome:
Verify that you do not have "Block third-party cookies and site data" checked in the Settings.
- Type chrome://settings/content
- Under the "Cookies" header, there is a check box labeled "Block third-party cookies and site data" that should be unchecked in order for ZMC to work correctly.
Make sure that add-on or extension that is blocking third-party cookies are disabled. To view what extensions and add-ons are installed:
- Click the FireFox menu in the top left corner.
- Click Add-ons.
- Click Extensions and note any extensions that may be blocking cookies.
3) Internet Explorer
Please follow the steps and check if you have the correct settings.
- Click Tools and then Internet Options.
- Go to the Privacy tab and click the Advanced button.
- Select Accept under "Third-party Cookies".
- Click the OK button to apply these settings.