According to your description it seems the NVR is failing to boot the OS, and probably the only way is to recover it by serial port. Please answer the questions:
- Was the NVR connected to the Internet using the default username/password?
- Do you have in the LAN working istallation of iVMS4200 or SADP search tool (using Winpcap)? Make sure you do a correct search for the device.
- For the RS232: do you use correct settings (115200,8,N,1,None) and correct serial cable?