I found the solution.
Entering by telnet, calling the DVR IP, in my case 192.168.1.140.
Then log on as:
user: root
password: xc3511
This worked for me, if not try these ones:
root xmhdipc
root klv123
root xc3511
root 123456
root jvbzd
default OxhlwSG8
defaul tlJwpbo6
defaul S2fGqNFs
root hi3518
(https://gist.github.com/gabonator/74cdd6ab4f733ff047356198c781f27d)
Then I just remove my two user accounts, as described on this video:
I turned off and on my dvr and BINGO!!!!
Thanks.