If you haven't done so yet, perform a hard reset to see if it will make any difference. You could do this by following steps in link below:
Dell Computer Does Not Turn On or Boot Into Windows | Dell US
Also, you hearing any beeps coming from the computer? Any blinking lights on the computer? If yes, see Device Status Lights (Diagnostic) in Dell Latitude E7450 Owner's Manual in link below:
Support for Latitude E7450 | Documentation | Dell US
