Why is it not charging at all?

@sreyoshiroshni I would replace the battery and the charging port again. Also, check the ribbon cable that connects the charging board to the main board. Those do come loose and even tear etc. If none of that works, the issue will be on your mainboard. Possibly damaged charging IC etc.

I would consider saving some money and to repair/open this phone by yourself. It is not that complicated. Check videos like this Replacing those parts is also straight forward.

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 a device with the same issues as you do. 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!