Buying cheap from China is like a lottery. Sometimes everything is fine, sometimes is not. For example, I will never again buy super motors and pellers. This just does not work. With electronics it is slightly better. Usually it works. But sometimes, well, it does not. And this might be a case for Flip32+ multirotor flight controllers from around June 2015 (give or take few weeks) v2.3_OEM RTF. In those FC, buzzer is not working when connected to designated pins.
Reason? Instead of 100Ohm SMD resistor in buzzer circuit, there is a capacitor. Solution is quite simple: replace capacitor with a resistor and fix manufacturing error.
What you will need, is a 0603 size 100R (100Ohm) SMD resistor and a (good) soldering iron. Position of faulty element is shown on a picture below.
Today I’ve fixed two of mine Flip32 flight controllers and succeeded on both. 0603 size SMD are small, but big enough to do it at home. If your soldering iron has temperature setting, set it to 280-300C. If not, use one with about 20-25W. And sharp, good soldering tip of course. To remove old SMD element just heat it up about 1 second and push away with a tip of soldering iron. Apply some new solder to pads. Place new element on pads, push it carefully with a needle when needed. Heat it for a second and that is all. New SMD element should be soldered to pads and buzzer should be working like expected.