I have the Verizon version of the V60, and the shutter sound option works as expected. No should when I take photos on it. As pointed out above, some regions require an audible shutter sound (you can thank people doing up-skirt type photos on unsuspecting women for those laws), but hard to say if that's the case here. If they went through the trouble to override that setting to comply with a law, I figured they would remove the option all together.
I would try first clearing the app cache to see if something is hung up in the code. If that doesn't work, try clearing the app data, but that also means losing all of your custom settings.
And just to be clear, you're talking about the stock LG camera app that was pre-installed, and not a third party app you downloaded?