@vzw_customer_support Sorry, I should have updated this post. Turned out , my iPhone 6s was indeed locked. I had to place an unlock request with ATT to move past this.
Now, I did have the phone unlocked a couple of years back. I still have the confirmation in my email. So I had assumed this not to be an issue. But working with the next Verizon tech support did uncover my 'real' lock status of the phone. I had to call AT&T to unlock my phone again. Kudos to their system that the phone was unlocked within seconds of me filing an online request.
Anyways, it should be noted that unlock requests may not be permanent if no action is taken for a long time.
Did you confirm with the previous carrier that your phone is unlocked from them?