I've got two batteries for my Phantom 4. One works as normal, it can be fully charged and works in the drone, but the other one can only be fully charged and will not power on. If I press the button once, all four bars light up, and in the charger hub a solid green light displays that it is completely charged. When I then go to use it in the drone however, I press the button once, and then hold it and the four bars light up in sequence but then a second later the four bars turn off and the circle button light stays on, but the drone does not power on. Any ideas on what's causing this issue?

Hello there. Sorry about the inconvenience.  Please check if there is any foreign matter in the battery compartment and the battery itself. If there is, clean them by wiping the pins with isopropyl alcohol.  Check if the metal connector outside the compartment and battery contact pins are misshapen or have poor contact. If so, we recommend adjusting them manually. If the issue persists after the above troubleshooting steps have been tried, we suggest you submit a request on the DJI official website to send the malfunctioning components back for repairs. You can use this link to submit a repair request: https://www.dji.com/global/support. Have a great day ahead.