Please follow the instructions below to unblock 3rd parties:
1. On the menu bar, click on the Firefox menu, select Options and select Preferences
2. Select the Privacy panel.
3. Set Firefox will: to Use custom settings for history – from the dropdown options
4. Make sure Accept Cookies from sites, and, Accept third-party cookies boxes are checked
5. Reload your CRM account.
You should now be able to play back your voicemail messages.