Sandisk Cruzer Glide 16GB, formatted to fat32. It was the third USB drive I tried. Also the dock showed a progress bar on my TV during the update, so that's weird that yours doesn't show anything.

I just bought another one on amazon. the dumbest thing ever, haha. I'll try out the new one in the morning.

my first USB that didnt work was a 3.0 drive. I got this USB which did the trick.

True, but a decent 16gb flash drive is $5. The adapter OP references is nearly $8. Boot drives don’t need to be fast. Sure it might take an extra minute to boot, but I personally only reboot mine for updates.

And the back up the $5 claim: https://www.amazon.com/dp/B007YX9O9O/ref=cm_sw_r_cp_api_i_2IAEDbTHQKFY2