Lots of posts elsewhere on this topic (e.g. https://github.com/arduino/Arduino/issues/9290) but can’t find anything here.
It appears the bootloader needs to be patched for Catalina and then burned onto Pro Micro using separate programmer.
The patching process is too low level for me to attempt but if someone can do this and post the necessary files I think I can burn it onto the board (using a Uno as programmer).
If anyone has done this, a step-by-step guide would be much appreciated. :roll:
Current config: OSX 10.15.1 running Arduino 1.8.10 with latest board files from GitHub (1.1.12)
Hi Robspark.
This is the first I’ve heard about this issue and unfortunately we here at SparkFun don’t have a fix for this. I would imagine Apple or Arduino need to come up with a driver so that OSX recognizes the board while in bootloader.
Changing the bootloader to work with OSX Catalina would probably only work until the next version of OSX comes out and would make previous versions of the board paperweights unless you have the tools and knowledge to reflash your boards firmware. Most Arduino users are not going to be tech savvy enough to change the bootloader on their own anyway.
Eventually I’m sure this will get resolved, but in the meantime sticking to a older version of OSX or using a PC or running Windows in a VM look to be the only solution.
A similar issue plagued FTDI based Arduino’s several years ago when Apple decided to write their own (broken) FTDI drivers but that eventually was cleared up when FTDI came up with a replacement driver for Apples. I imagine this issue will likely follow the same path.
That being said, if anyone has a workaround until this gets properly fixed, please post the steps needed or a link to steps if you know of any. 
Thanks TS-Chris. I don’t pretend to understand the low level stuff talked about in other threads but hacking the boot loader seems to be the current workaround. I’ll keep researching and will update if I find a workable solution.
Pololu have already posted a patch and instructions… https://www.pololu.com/docs/0J82
Thanks for the link Rob.
Let us know if it works for you!
Good news!
Burning the Pololu-patched Caterina bootloader to the Pro Micro 5V restores upload capability from OSX Catalina. I’ve not noticed any unwanted side effects as yet.