Unable to sign in iPhone although i have another iphone id

A message saying, “The maximum number of free accounts have been activated”, is discussed in the support document: If you see “The maximum number of free accounts have been activated” - Apple Support

Apple apparently limits excessive Apple Account creation, or iCloud activation of web-created accounts, on any one device per year (presumably a 12-month period). Your options are:

1. Use a different account that has already been set up on a device previously,.

2. Set up the account on a different device that hasn’t reached this limit (you can then use it on the device that displayed the message previously).

3. Wait until the time limit has passed.

I am also concerned that the phone may not have been properly prepared for sale. The previous owner should have done the things in this article What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support and The All Too Common SAD Reality of Buying … - Apple Community and If you want to buy a preowned iPhone - Apple Support