First ensure the issue isn't with the power source or socket you're using - you can quickly check this by plugging your phone into a different outlet, then checking if it charges. If the socket is not the issue, try taking a closer look at the power cable or charging port on your phone, ensuring everything appears as it should. Then, try turning your phone off completely and plugging it into the socket - bear in mind if the battery is completely drained, it might take up to 2 or 3 minutes to start charging.