I am trying to get wsjtx to run on a new iMac using Monterey OS and M chip and a Yaesu FT991 transceiver. I am confused about whether I need SiLab drivers or not. I've searched Google and watched several videos, but none seem to address my problem. WSJT opens and displays signals but the CAT control doesn't work. Audio codec shows in both wsjt and the mac preferences. A SiLabs driver shows in the Mac extensions, but it says "not loaded". When I click on "Test CAT", a diagnostic flashes on screen saying "resource busy". On the Radio Settings menu I see nothing that identifies a SiLab driver. The serial port choice that seems most likely shows "/dev/tty.wlan-debug", but that doesn't look very promising. I am using a single USB cable to connect the transceiver to the mac. It works fine on my old macbook pro, so I suspect I'm doing something really dumb, but can't figure out what. Suggestions welcome and thank you.