iPhone battery not charging when connected to charger

Try cleaning the charging port. You’d be surprised with the amount of lint that can get there.

I recommend bringing it to Apple, but if you prefer to do it yourself, be careful not to scratch it. And do not use metal to clean it.

A thin toothpick is a good bet, in my opinion. But make sure it easily fits in the port.

When you plug the charger into the phone, do you hear the soft "chime" sound?

If no, can you try another charger and/or cable?

If yes, what happens of you leave the charger connected for 20-30 minutes?

What is the Maximum Capacity of the battery? Settings > Battery > Battery Health

How long has it been since you replaced the battery?

No chime means that the charger and or cable is not making a good connection to the iPhone, or the charger / cable is not working correctly.

What happens if you try another charger or cable as a test?

Looks like you will need to replace the battery in the next few months when it drops under 80%