Just to help troubleshoot, why did you change the charge port, battery and screen?
Can you plug it into a USB ammeter to see if there is any current flow?
Replacement charge ports and batteries are notorious for low quality. You may have a defective replacement part.
Otherwise, a bootlooping device can be caused by many things. Give us more history by commenting on this answer.
A few things to consider:
- Try a hard reset (Home & Power button for 10 secs)
- Use a genuine Apple Lightning connector
- Use a genuine Apple charging brick and let it charge overnight
- Try to connect it to different computers with iTunes if possible
- Put the phone in recovery mode (search DFU Mode). Careful, this can reset your data so only do it if you have a backup.
- If you want to get deeper, disconnect the screen assembly and see if iTunes will recognize the phone.
Otherwise, you may have a logic board issue. If you are uncomfortable doing these steps, consider finding a repair shop to do the troubleshooting. A shop that also does micro-soldering can go deeper if the problem is not modular in nature.