trubel wrote: ↑Sun Apr 15, 2018 7:26 pm RESOLVED

Answer is here https://www.dfrobot.com/forum/viewtopic.php?t=216
My steps
Load blink into arduino ide. Select leonardo. The Leo usb won't appear yet/still.

press Arduino reset button. Leo usb port will momentarily appear. Select it quickly and try to upload. But by the time blink is compiled, it can't upload because the usb has disappeared again. Persevere.

Using the same setup as your first (failed) attempt, click upload again. Wait until the compiler has almost finished, then press arduino reset button again. Just as the ide starts to try and upload, your Leo usb port momentarily reappears again, long enough for the upload to succeed.

Your Leo port will now appear in the dropdown menu again! Permanently...until the next time