Hi James,
According to your description, it seems this issue is more related to the Internet Browser settings.
For this issue, I suggest you try to browse SFB control panel URL in another SFB Server’s browser to check whether could open it.
Then please make sure you have added the URL into the trusted sites in IE, and ensure “Run ActiveX controls and plug-ins” is set to Enabled. In addition, please also check the proxy settings in the IE. Details about this you could refer to the official document:
Troubleshooting Lync Server 2013 Control Panel.
Best Regards,
Evan Jiang
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