I found the solution on my own, and with help from users on the OnePlus.net forums. There is a HUGE oversight in the tear down and screen replacement guides on here involving the possibility of the cellular antenna coming loose from the motherboard. Without knowing it was even there, I simply forgot to check the connection, which was indeed not connected.
Here is an illustration to help others (notice the cable for the antenna is the gold connector cable that the tech is pointing to with the spudger(sp?):
https://d3nevzfk7ii3be.cloudfront.net/igi/EjAVJtVZoJ2NGtYb.medium
Hope this helps others.