Note 9 not unlocking

@steve3384

Awesome information.  I’m marking as correct so others will find it quickly, even though it may not be the only solution.  

To all, if ATT isn’t cooperating, file an FCC complaint and then ATT will have someone higher up the food chain contact you.  

@steve3384, I had HIGH hopes when I read your post. I had already received my 16-digit code, used a T-Mo SIM and still received an "incorrect code entered" message. I had even tried entering the code using the no-SIM method and that failed. So I then put in a Verizon SIM and unfortunately also got an "incorrect code entered" message. 

I've never had this issue before using non-active SIM cards. Were your SIM cards active? 

I have not received any message that I have only "one more attempt" and do not even know if I am actually locked out because a couple of AT&T CSRs had me try the codes again after I had already done so 4 times. 

lizdance40, following your advice I had filed FCC complaint.  Few days later received a call from a representative of AT&T Office of The President.  Wonderful person.  Pleasure to deal with.  Follows on calls.  Has direct access to the Intensive Care Team.  The issue has not been resolved yet, but we are working on it.  World of difference comparing to the service for front line AT&T Support.

As to the reasons why the issue has not been resolved:
I have received two AT&T updates on my phone in the last month or so.  Hoped they would take care of the issue.  They did not.
It is established that the SIM card unlock code has 16 digits.  However, the field to enter it accepts only 8.  This is also confirmed, and could be easily validated: when you enter the unlock code the last entered digits is displayed for a couple of seconds before turning to a dot.  This behavior happens only to the first 8 entered digits.  After that keyboard does not react on the additional entered digit.  None of the entered digits after 8th shows on the screen.
On the keyboard there is a backspace key.  If you hit the key, the number of dot decreases.  It proves that there is no horizontal scrolling.  This is not a case when only 8 dots are shown, but additional digits are still accepted, but scrolled.
Until phone's firmware and/or Operating System are changed to accept the 16-digits unlock code, the attempts to unlock the phone would be unsuccessful.