Cannot accessor ping my fortigate 30D

Hello Experts,

I have a FortiGate 30D device at our remote location. I restarted the device by unplugging the power cord. Ever since I restarted the device I am unable to ping its IP address. Also, I am unable to access the GUI. Can someone please tell me how I can access the GUI or at least find out what is the new IP address if it has if it has changed?