I recently installed a RAM on the server(T420) everything runs smoothly then after 4 days I wasn't able to Remote the server, tried to connect a monitor a " No Signal " popup on the monitor tried different monitor and VGA cable still no display, tried to plug in a usb keyboard and mouse but in doesn't power up. But the server is still up and running, I can still access the shared folder thru network, I can still access iDrac via browser. Should I do a cold reboot ?