No sound to TV via HDMI

To start off, I have a 13" Macbook Pro (mid 2012), so the output via MiniDisplay is supported. Recently my volume in the top hover bar has become detached from the actual volume keyboard controls. Ie. If I mute the sound using the key on the keyboard, the speaker icon in the top hover bar is supposed to show that it is muted. It doesn't. This wasn't a problem because it was still responsive, just the top bar wouldn't show the change. However, now that I plug my HDMI cable in (through an adapter of course) for my TV, the sound will only play through my internal laptop speakers.

I have tried:

Unplugging and replugging the adapter back in

Restarting my computer

Turning the TV off and back on

Relaunching the Netflix webpage (for example)

Settings > Sound > LG TV

It should be working for all intents and purposes, because I've tried EVERYTHING. It has worked up until recently, so it's nothing with my computer permanently that I can think of. I updated to Yosemite but that wasn't the beginning of the problem and has worked fine up until now. I really don't know if it's a problem with my adapter, but if it is I'll buy a new one. It's just a hassle. HELP!