Resetting connection on Itsysbitsy M4

Been trying to sort out a problem i’m have with Istybitsy M4 that it keeps resetting itself after 32secs and reconnecting with the laptop.
Have tried seven different Itsybitsy’s with 5 OK and 2 appearing to be DOA with this reset problem

Below are the links to the querys on the adafruit forum.

https://forums.adafruit.com/viewtopic.php?f=62&t=157280&p=776496#p776496

https://forums.adafruit.com/viewtopic.php?f=62&t=156475