Invalid Sim on Refurb Galaxy S7 SM-930T

Picked up a refurbished S7 from a reputable closeout/deal vendor and had it delivered a couple days ago. Went ahead and flashed the the most current 7.0 firmware on it with Odin without issue (G930TUVU4BQF6) only to find out today that it doesn't work with my brand new nano-sim.

I purchased the nano-sim today at a T-Mobile store and the salesperson confirmed that it worked with his phone. I also tested it on my old T-Mobile branded Note 3 with success.

The S7 will only show "Invalid Sim" without any explanation why. I tried flashing back to stock, but I get some aboot error even though the baseband is the same.

I'm about to return this thing and order a brand new S8, but I'm still curious if it was something I did or just the phone was a lemon. Do they even have sims on hand to check for function during refurbish process?

TL;DR: Flashed to most recent firmware, phone says invalid sim, sim confirmed working in other phones. What else can be done before returning the phone?