Hello! I've been searching these boards for 30 minutes for the answer to this (I'm sure it's fairly basic) but I've been running Arduino / Teensyduino successfully for a few years on my MacBook Pro with Mojave. I decided to upgrade to Catalina today (10.15.7) and my old sketches wouldn't open. Maybe it was a documents permissions issue but I decided a fresh install of Teensyduino couldn't hurt. Now when I open my sketches (even the most basic example Teensy sketches for USB.MIDI) they won't compile.

I'm sure it has to do with a missing library or something but I'm not sure what's where at this point. I can see all my sketches from before but I can't get them to compile (like it's not seeing the Teensy functions) because it throws an error on anything that's native to Teensy.

Thanks in advance for any ideas!