For newer DVRs (post-2018), many manufacturers require a “password reset file” generated via their support portal. You will need the DVR’s serial number and proof of purchase.
Most H.264 DVRs ship with a factory-default username and password. If the device has never been configured, or if it has been recently reset to factory settings, you can gain access using common default combinations.
Common Default Usernames and Passwords:
Note: Often, the username is "admin" and the password is simply left blank. Try pressing "OK" without entering a password first.