Some newer Dahua NVRs have a USB reset procedure:
Suddenly, you are locked out of your security footage, unable to add new cameras, adjust recording schedules, or export evidence. Whether you are a business owner dealing with a former IT manager who left no credentials, or a homeowner who hasn't logged into their system in two years, you are likely searching for a way back in. how to reset dahua nvr admin password
Once you regain access, do these three things immediately: Some newer Dahua NVRs have a USB reset