Here are some things you can try: 1) With the charger plugged in, press and hold the power button for about 10 seconds. Then press the power button again. If the machine still does not power on, move onto the next step 2) Attempt to reset the SMC. After resetting the SMC, attempt to power on. If you still aren’t able to power on, move onto the next step 3) Try using a separate known-good charger. If you don’t have access to a charger you can take it to a tech shop and ask them if they can try to charge it as a free service. If it charges using a separate charger there may be an issue with your charger and it might need to be replaced. If none of these steps work for you there may be a hardware issue with your machine. If that’s the case I would recommend having it diagnosed by a Mac repair shop. If you’re feeling adventurous you can try disconnecting and reconnecting the battery, but be forewarned that these models can be a little tricky to open safely. Here’s a guide for accessing the battery.