It’s driving me mad! So mad, I don’t think I will ever get another Mac, I’m so fed up with being harassed to upgrade and then finding that important things no longer work, sometimes Apple’s own software. Now it is my USB music keyboard, and my Nifty mini drive. The MacBook can’t see either. It is not the SD card, I bought a new one, hoping it was that. And it is not the keyboard, still works fine with my ancient IMac running El Capitan. But this is really a bit slow to use now. And GarageBand has gone mad too, disables MIDI and other things on startup. And it is not the USB ports, they still work with printer and hard drives. I have spent nearly 3 hours on the phone with Apple support and we’ve done all the usual troubleshooting, including downloading a new version of GarageBand. The only thing left to try is taking it back to El Capitan and remaining stuck on that forever!! Any suggestions would be appreciated. I don’t want to go back to an old operating system.