The battery is excessively worn and has been completely damaged
Generally speaking, this kind of situation is rare. You can check the battery health through our education. The battery health of an iPhone in normal use is above that of an iPhone in one year, and is normal in more than two years. However, if you use it for one year and it has already fallen, there are only two possibilities. One is that you have bought a fake, and the other is that you often commit the battery damage behavior mentioned in the previous chapter. I have seen people who charge their batteries several times a day because they play card games, but the health of their cell phone batteries has dropped in less than half a year.
Battery management ic damaged
This is mostly due to the mobile phone falling on the ground, which leads to the main board component desoldering. The probability is very small. If the battery cannot be charged and the motherboard is damaged, the store will charge you for replacing the motherboard. In fact, only the power supply IC needs to be replaced.
The gold finger of the charging port is oxidized or dirty
Scratch the golden finger part of the charging port on the iPhone with the sim card pin matching the iPhone, and try to scrape some oxide off the top.