I am assuming that the programming cable you have was manufactured
with and unauthorized copy of a Prolific USB-to-TTL chip. The device
driver written and supplied by Prolific (the chip manufacturer) is
designed to be incompatible with counterfeit copies of their chips.
The simplest solution to get you going should be to get an FTDI chip
based programming cable like the PC-04 from Baofeng Tech (the radio
dealer in the USA). My understanding is that the native Apple FTDI
device driver is recommended for FTDI chips. Baofeng Tech sells direct
on their website and also via Amazon, so with an Amazon Prime
membership you could have a PC-04 programming cable in 2 days.
https://baofengtech.com/pc-04-programming-cableA possible solution to use the programming cable that you already have
would be to purchase a device driver from a 3rd party. I have read
where the device driver from the link below has been used successfully
with programming cables manufactured with Prolific type chips. It
costs EUR 7.90 (about $9.00) and you would be able to download it
right after purchasing it. They do offer a money back guarantee if
their support can't get you going.
https://www.mac-usb-serial.com/Here is their page for OS X Serial Driver Installation
https://www.mac-usb-serial.com/docs/support/installation.htmlGood luck,
Jim KC9HI