I just went through the reactivation process. Had to download the NBC Sports app. Then had to put in the activation code online that was displayed on my TV from the new app. Process worked fine. I have no FS content on my TV but do on my computer. Was able to play the videos after it recognized I had a figure skating pass already, (it told me to sign up for a pass).
Did your firestick prompt you to download the new app? Did it give you a code to put in online from your computer?
ETA: Uh, I should point out I have Roku
I did not download a new app. Does new app say nbc gold