Solved
Samsung Smart TV UN55TU700DF does not recognize ROKU stick and will not connect
When I turn on my Samsung Smart TV with the ROKU stick connected to HDMI1 or HDMI2 it says it is unknown and will not connect. There is a little red button beside it that looks like an on/off button,...
You lose me at “little red button beside it that looks like an on/off button”. But… I assume the Roku is powered up? (Generally, you want it to be powered by a USB/AC adapter connected to the wall – sometimes a TV USB can work – but not always.) Have you tried pressing buttons on the Roku remote? Ie: try the Home key. Some Rokus have a sleep/low power mode that does look a lot like “off”.
You're right in thinking that the indications are that the Samsung recognizes a new device connected but powered down. I believe you should have an external power supply for that 3810X. Check that.
