Edit: Also works for NO POWER.
Seems that many online are having this same issue. They can pair the Bose Mini II SoundLink to their Macbook Pros but they cannot hear any sound. Even worse, you see the SoundLink listed in the Bluetooth window but see nothing in Sound Presences. Most were told to clear the SoundLink of all paired devices (Holding the Bluetooth button down until cleared), unpairing and pairing again, restarting your Macbook Pro. And, surprisingly, it did not work.
After spending nearly 24 hours on this fix, I finally found one on the Bose website. It was clear as daylight. You needed to reset your Bose speaker by holding the Power button for roughly 10 seconds or until the lights all turn off. You can then re-pair on your Macbook Pro and your speaker will pop up in Sound Preferences.
It also works if you have no power.
I am pretty sure that is all the Bose repair shops did was a reset.
Now you know.
I realized the issue was the Bose Mini II SoundLink speaker after I connected my PowerBeats Bluetooth headphones to my Macbook Pro and could hear sound.
I hope you can find this article in the search engines to avoid the headaches of not having sound. :-)