Can you provide some additional information? What brand and model TV? Does it reach the Roku home screen, or is the boot constantly restarting before reaching the home screen? Have you attempted a soft reset (pulling the power, wait five minutes then power it back up)?
Dan Ultra (4640), Ultra (4670), Ultra (4800), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.