Forum Discussion
I just experienced a similar problem with my Roku Ultra. I am not using a SD card. I disconnected the power source, HDMI cable, and ethernet cable for 10 minutes, and the problem still persists when i reconnected the cables. The bouncing Roku letters displays for about two seconds and then a blank screen.
Whodidit1175, first, try it on another TV just in case it's some kind of HDMI issue.
I would suspect a bad box or a bad power adapter. If it's still under warranty:
Step by step instructions for returns and warranty replacements | Official Roku Support
If it's not, you could try a factory reset, although if it's dying in 2 seconds it's not likely to work. With the power connected, press and hold the reset button for no less than 30 seconds.
If you have an identical power adapter from another Ultra, give it a try. Your last option is to buy a new power adapter and hope that was the problem or that you can return it if it doesn't fix it.