Installing the silabs Silicon Labs VCP Driver.pkg worked for me also. 👍 (on OS X 10.11.6) Seems obvious that we need the drivers, but I thought I already had them after going thru the espressif/arduino-esp32 install steps. e.g. My "System Report / Hardware / USB" showed CP2102 USB to UART Bridge Controller driver For others' future reference, you should see something like: n8s-iMac:nleon$ ls -al /dev/tty.* crw-rw-rw- 1 root wheel 18, 2 Jul 4 11:14 /dev/tty.SLAB_USBtoUART Regardless, thanks for the pointer! Admin Apps4Rent