Closing Connection with BSL

Hello,
I'm new with panstamp environment.
For this reason i tried to compile an existed sketch for panstamp
I have Panstamp NRG 2, when i upload the sketch, I get:

Connecting to target board
Erasing main flash...
bsloader.BslException: No response received from BSL
Trying again...
Closing connection with BSL...

Please, I need help for this problem
Thanks in advance