As we know, for the iPhone activation problem, first we need to check SIM card and Apple ID problem.
- Check SIM card
Make sure the SIM card is working perfectly; you can remove the SIM card from the iPhone, and then install it again. After checking, we know the SIM card in this iPhone 6S Plus is normal, which means it's not the SIM card problem.
- Check Apple ID
When you want to activate the iPhone, if it asks you to sign in with an Apple ID, then please sign in your Apple ID, the Apple ID is signed in successfully, but this iPhone 6SP still won't activate, then we need to check other problem.
Next, resort the iPhone 6S Plus, after restarting, try to activate the iPhone again, it's still failed. Now, connect iPhone to the computer via iPhone Lightning Cable, and then use iTunes to activate it, but it's also failed.
After restoring the iPhone 6S Plus, the iPhone still can't be activated; now we can exclude the software problems, so we need to check NFC and SN/BT/WIFI match or not problems.
Use phone opening tools to disassemble the iPhone 6S Plus, remove the iPhone display assembly, disconnect the iPhone battery, and then take out the iPhone motherboard, and observe it under the microscope, we can see that the iPhone Nand flash was repaired before, and there are some tin balls around the NFC.
Attach the iPhone motherboard to the PCB holder fixture, use Quick 861DW hot air rework station and tweezers to remove the NFC.
Apply some Soldering Tin Cream to the solder pad, and then install the NFC IC back to the motherboard.
Hope the above methods will help you. If you have other questions about iPhone phones, please leave a comment under the comment.