Arduino UNO don't (always) connect

Hi guys,

Here is the trick : I just bought an Arduino UNO (my first one).
I installed last version of the Arduino software (1.8) with the USB pilotes.

BUUUUUT when I plug my Arduino, the green light "ON" remains brilliant during few seconds, then collapse... I can't upload anything, it's not available under Arduino software and the "Ports" menu is disabled...

Sometimes it works after a reboot, sometimes not.
And I work under Windows 7.

Help would be gladly appreciated.

All the best,

Florian

if your green light turns off then probably there is a problem with your board and check if you have made the connections correctly perhaps the light collapses due to a short circuit which means connecting ground to the 5v and 5v to the ground

seems you were right... Thanks a lot !