Try a reset:

1. Disconnect all peripherals: printers; USB devices; media cards; USB hubs and extenders; etc.
2. Disconnect the AC adapter.
3. Disconnect the battery.
4. Press and hold the power button for 30 seconds to discharge any residual electricity.
5. Reconnect the AC adapter (without connecting the battery)
6. Reboot the laptop.

Check if the light is lit at the plug end of the AC adapter or on the adapter block. And see if that light remains lit when you plug it into the laptop's jack. If the AC adapter's light goes dark when you plug it into the laptop, then the fault is likely with the jack or the circuit. 

Hold F2 while booting, to enter BIOS. See if the AC adapter is recognized.

If it starts up, run Dell Diagnostics:
Press and hold F12 while booting to enter the One Time Boot Menu, select Diagnostics and press Enter. The Dell Diagnostics will test major hardware components. Choose to run extended tests.

And, please tell us what model laptop you have.

Perform a hard reset.

1. Turn off the computer.
2. Disconnect the AC adapter or power cable from the computer, and remove the battery (for Dell laptops with removable battery).
   NOTE: For Dell laptops that have a nonremovable battery, see the Dell knowledge base article  How to reset Real Time Clock (RTC).
   For Dell laptops with removable batteries, see the  User Guide for your Dell laptop for step-by-step instructions to safely remove the battery.
   NOTE: On select Dell Latitude laptops, try to recover the laptop using the forced ePSA method from a POST or boot failure. To learn more, see the Dell knowledge base article  How to Use Forced ePSA to Recover from POST or Boot Failure.
3. Disconnect all devices such as USB drives, printers, webcams, and media cards (SD/xD).
4. Press and hold the power button for 15 to 20 seconds to drain residual power.
5. Connect the AC adapter or power cable and the battery (for Dell laptops).
6. If your Dell computer can turn on but is unable to boot into Windows, identify the symptoms and follow the appropriate troubleshooting guide.
7. If your Dell computer is not able to turn on, follow the troubleshooting guide for no power symptom