Every time an iPhone is restarted then it requires the passcode to be entered and then Touch / Face ID will takeover until the next time the iPhone has to be restarted. Having said that, you probably got home and started the iPhone which was probably OFF. Now it needs the passcode to get to the home screen. The passcode that the seller gave you does not work. The seller has given you an incorrect passcode.
Two Options here:
- Return the iPhone to the seller and be done with it.
- Reset the passcode by connecting your iPhone to a Mac or a Windows PC with iTunes and follow this procedure ➔ How to reset your passcode on a disabled iPhone.
If you choose option 2 then I have a good feeling that you will run into Activation issues and you will need that seller again to provide you with the appropriate Apple ID and Password.
I recommend that you either get the correct passcode (Option 1 above) from the seller OR return the iPhone and get your money back.
Axel F.