I want to use my original Mbox in Logic Pro 10.4.3. How can I do this?

I used the M-Box from 2009 to 2016. I'd just plug it in, turn it on, then start Logic Pro and the interface was automatically recognized instead of the internal sound card. I don't have Logic open right now, but if the program doesn't recognize it right away then you can switch the audio source in preferences as well, I believe. Just make sure the output is the M-box, then if you're using any inputs switch that as well.

Preferences > Audio > then you can change the input and output sources to M-Box? Other than that, the only thing I can make sure to tell you is to try to make sure the drivers you're downloading with Avid are the correct ones.

I also have core audio checked under this tab, but I'm not sure what that affects.

Good luck

This may works:

https://www.usb-audio.com/download/

This is a paid driver. Not cheap! You can try a demo to see if it works.

Good luck.