This assumes that Adobe Flash Player is installed correctly and you can view Flash content elsewhere. If this is not the case, please ensure you have the newest version of the Adobe Flash player, and that your browser is also up to date as well.
If you are having one of the issues below, following the steps outlined should resolve the issue. This should actually be easily adapted to any website that may have this error.
Click the menu button in the upper right of the browser and then click Add-ons as highlighted below:
That will take you to the following page, and the only setting that can be changed is to set it to always activate. If you are having playback issues, change it to always activate.
Once you have made the change, you can close the tab, and then click the menu button and then click exit to close Firefox completely, so that the change can take effect. When you reopen it, you should not have any further issues.