That suggestion should probably be stricken or nuanced. I see that the instructions on the Parallax web site page for PropellerIDE specifically recommend downloading the FTDI version of the driver. The name and exact location of the Apple driver on pre-Sierra OS versions is different though. Keep the Apple FTDI driver, which on Sierra is located at /System/Library/Extensions/AppleUSBFTDI.kext.

Delete it using Terminal from /Library/Extensions/FTDIUSBserialDriver.kext. If you look in the system report under USB, you will probably find that the same VCP serial port is listed twice. The only way to get another try is to move to another physical USB port until that gets locks and so on. The symptoms are that you will be able to use the port once, but then if you disconnect the dongle and then come back to it or try to use another one on the same USB port, you will find that it is locked. If you then go and download install the FTDI version 2.3 VCP driver directly from, the two will conflict. The issue is that Apple, starting with OS X Mavericks (10.9), has included a driver for FTDI serial ports along with the system install. I hadn't seen this issue mentioned here and it took some hair tearing and googling to figure it out. (Thanks, Brett, Steve, and Parallax!) Initially I had a problem with the FTDI serial ports, including but not limited to the Prop Plug and my own FT231X boards. Since upgrading to OS X Sierra 10.12, I've started using PropellerIDE.