Do not use a generic H.264 firmware. Wrong firmware will brick your DVR. Look for a file named update.bin , dvr_firmware.bin , or TV_NVR_xxx.img .
Nearly every TrueView DVR sold in the last 8 years has a physical "Reset" button located directly on the circuit board. You do not need to be logged in to use this. trueview dvr password reset
This works like resetting a computer motherboard. Do not use a generic H