When Apple released its new Mac OS Sierra, it made some change to the driver structure, making All Arduino-compatible Boards with CH340/CH341 including Makeblock's products fail to work. After communicating with WCH engineers, Here's a solution (It's still in the beta stage, so it'll be the best to not upgrade to MacOS Sierra at the current stage).
if you've used Makeblock's products before you upgrade your os, you need to open the "Terminal" App, run the following command followed by an enter, and enter your user password followed by an enter. (be sure to type the exact same command - we're deleting drivers, a typo may have grave consequences):
sudo rm -rf /System/Library/Extensions/usb.kext
If you've never done this, you may need to change your "Security and Privacy" setting in the System Preference. Change "Allow Apps Downloaded From" to "Mac App Store and Identified Developers" or "Anywhere"
- download and install the new driver for CH340