This could have also been an issue where I needed to activate on some other phone before transferring to a Nexus 5X in order for me to get it to work.
Verizon is known to be the most restrictive carrier in the US as far as allowed devices.
I had a testing phone and my regular phone, I kept swapping the same Verizon SIM between them. It worked for maybe 3 swaps, then Verizon blocked my account and sent me an email: suspicious activity detected, the SIM is blocked and cannot be restored, the contract has been terminated, you will receive the refund in mail.
Good riddance, US Mobile is so much cheaper and pleasant to use. I am scared to swap SIMs with them now though.