Why is it not opening

@bibeakchan75754 first you want to check your charger. Make sure it has proper output. Then check your charging cable. Check to make sure the connectors are not bend etc. After that, check the charging port. Clean it of any debris etc, use a few puffs of air to clean it out. If none of this works, get a USB ammeter and see if your phone draws any amperage from the charger. If it does not, it is possible that this is a charging port issue or a bad battery.

To check the charging port, use a voltmeter and measure the voltage on your battery connector. Next plug your phone charger in. Now measure the voltage on your battery connector. That voltage will have to have increased. IF not then the issue is either the port or the charging circuit.

You also want to check the flex cables coming from the charging board to the main board. Check that for micro tears and corrosion and proper connection to the boards. I suggest that you start with a new battery if any of the above did not work. After that it's the charging board and flex cables.

Since iFixit does not yet have specific guides for this use this video for the battery and this one up to 3:06 for the charging (Sub_)board]

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same issues with their phone. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!