Hi !
I used in a program the LowPower.sleep. Uploading a new version of the program resulted in communication errors.
I read that the solution is a double click on the reset button. However that did not work in my case.
It seems that you have to do the double click at the right moment:
When you try to upload a new program you will see normally the following messages:
-->
...
Touching port /dev/cu.usbmodem1D1331 at 1200bps
Set DTR off
Flashing with command:/Users ...
<---
Try to do the double click quickly after the message "Set DTR off" appears. That will be just before the flashing occurs. The flashing will otherwise time out after half a minute or so if the device is in sleep. Doing the double click right now get the device out of sleep - I think !
Good Luck