I chatted with T-Mobile and agent said they sent the email on Feb 5th but there was nothing in my inbox.  He re-sent and didn't get the email.  He then called me and connected me to T-Mobile Rebate Team. The agent there walked me through ordering the TV with a code. I placed the order and received the TV last night.  Make sure to check the status of your reward.  Mine said Approved and I had to provide a screenshot of that. 

TV info:

SKU number 4K50N400A

Amazon Fire TV 50" 4-Series 4K UHD smart TV, stream live TV without cable

https://www.amazon.com/amazon-fire-tv-50-inch-4-series-4k-smart-tv/dp/B0B3GTSQ9Q#tech