Three suggestions based on the experience of other Citrix users with Firefox 30: '''(1) Change the plugin permission.''' Firefox 30 switched most plugins from "Always Activate" -- allowing any site to use them -- to "Ask to Activate" -- requiring sites to get your permission to use them. For some plugins, this setting does not work well and you need to change it back. To do that, open the Add-ons page using either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Plugins. Look for Citrix and change "Ask to Activate" to "Always Activate". Then try Citrix again in a new window (or exit and start Firefox up again). See: [https://support.mozilla.org/questions/1005678 Updated to Firefox 30.0 now Citrix Receiver will not open]. '''(2) If you have an older version of the plugin, you may need to update.''' See: [https://support.mozilla.org/questions/1005650 Firefox 30 will not launch the ICA Application when using Citrix receiver 4] '''(3) Check that Citrix content is using the desired plugin/application.''' See: [https://support.mozilla.org/questions/1007249 Using Citrix Receiver with Firefox 30 to connect to VDI it fails.]