Activation Lock

As I have forgoten my passcode I had to reset the phone, after reseting it via iTunes I am required to enter my Apple ID and password. I have an Apple ID and can open iCloud or Apple ID settings but cannot unlock/activate the phone with it. Find my phone is not actuve. Message is all the time: this Apple id cannot be used to unlock this phone.

I am the first and only owner of this phone so I need any support what to do next? Can I get somehow in a secure way confirmation that I am using the right apple id to unlock the phone?