If your DVR is beeping once around 30 secs, it's most likely constantly rebooting and unable to start up. Most likely the DVR is faulty.
It could also be due to a corrupted firmware due to various reason, e.g. Update failed, wrong firmware used for updating, faulty rom leading to corrupted firmware, etc. If it's under warranty, we can send it back to the manufacturer for repair. If it's not under warranty, you can search online on how to flash the firmware to attempt to repair. As the results is not always guaranteed to fix the issues, we do not provide re-flashing of firmware for bricked DVR/NVR. It'll not be economical for the customers as a service fee is chargeable regardless if the equipment can be repair.