ethernet ssh - putty - blank passworkd does not work

Hello,

I have BBB (beagle board black) correct IP address.
I use in with Putty SSH, with default port 22.
Putty connects to BBB and asks for
user: i enter root
password: I leave it blank

It says password incorrect.
any idea why ?
Thanks in advance

PS1: i tried other passwords such as Angstrom or Administrator, it does not work
PS2: Putty only works on my laptop if I log as root.

As I recall, I used “root” password “root”

I had tried also root as user and root as password and it did not work.

without putty, and using the miniUSB as power,
I can ping it, or copy file from or to it (using scp).

However, when i take off the miniUSB and instead use the power cable, (after reseting too)
putty do not work anymore:, i get this feedback from BBB:
ssh_exchange_identification: Connection closed by remote host

any idea?
thank

Blank root password is not allowed for the ssh connection. Check setting for a ssh server