I have an early 2011 Macbook Pro running 10.12.6 that just started pushing sound to the laptop speakers when sound originates from crunchyroll.com on Firefox 55.0.3 (64 bit). All other sources of audio (including other websites, iTunes, VLC and more) project from the external monitor. What setting did I screw up and how can I fix it? External monitor is a Vizio E320-A0 connected by an adapter and HDMI cable.