Uno R3 Not Displaying on Mac running macOS Mojave

Hi - I'm completely new to the Arduino world and I've scoured the internet looking for a solution. I have the Arduino IDE software for macOS installed (1.8.12) and I'm running Mojave. No matter why I do or try I can't get the Uno R3 to display on my computer and I've tried everything else in this forum and elsewhere (installing new drivers, uninstalling those drivers, inserting and restarting instead of hot inserting, disabling system safety features etc.)

I don't have a USB 2.0 hub to try if USB 3.0 really is the problem. I only have two USB 3.0 ports on my computer (2014 MacBook Pro). My wife has a slightly newer Mac and it won't display on her computer either (again, 3.0 ports only).

I'm using the Elegoo Uno R3 specifically (ATMega328P, Mega16u2) and I have also tried two different USB A-B cables and I'm certain one is is rated for data.

I have a solid green light on the board and a blinking orange light. I have checked that the cable is firmly inserted into both the board and the USB port.

I'm willing to buy a USB 2.0 hub if that will fix my problem, but I just wanted to have some level of certainty buying some outdated hardware will fix my problem :frowning:

Thanks in advance for any help you can provide!