iCloud Locked iPhone 6s

Good night,

I had a customer with a water damaged iPhone 6s which was not turning on. After working on the board we realized that the backlight circuit was the issue. Therefore, we were able to fix this and restore the phone. However, the customer forgot his passcode for the phone. So i restored the phone on iTunes. After restoring the phone its on activation lock. Customer also forgot his Apple ID password, however, he remembers his Apple ID. When trying to forget the password it is asking for a verification code, however, after putting in the verification code that was sent to his cell phone. It is asking for his passcode on the phone still. Please advise me of how i can fix this issue.