If you’ve installed TWRP on a rooted 1st-gen Fire TV and have run into the looping/blinking issue that some have experienced, there is now a partial fix that should allow some of you to get into TWRP to flash the pre-rooted Fire OS 5 ROM. The fix is only available for devices with an unlocked bootloader for now. Rbox told me he’ll be out of town until next week, so he won’t be able to make the fix compatible with all 1st-gen Fire TVs until later. While working to get to the bottom of the looping/blinking issue, rbox also managed to correct the issue causing incompatibility with 720p displays.
If you have a Fire TV 1 with an unlocked bootloader that has the looping/blinking TWRP issue, head over to this link and download