Rooted nexus 5 unable to register on AT&T

[Jakedo508]

I purchased a used N5 from eBay. It was apparently rooted already. The sim won't be recognized and the network won't register. I learned how to un-root and performed those steps last night. It gave me the option to lock up the phone but didn't want to seeing how it still isn't on the network. 2 questions......
1. Should I have locked it on the unroot?

2. Is there something else I can do before I rip this guy on EBAY a new one?

Posted via Android Central App