I tried unplugging the device for several minutes and swamping out the HDMI cable - got nothing. Then, I attached it to another TV and it worked. However, I re-attached to the original TV and it's staying it's not supported - this is after over a year using it on this TV - strange.
Can you provide us with the following information: -TV brand and model number -Roku device model -serial number -device ID -software OS/version (these can all be found in Settings > System > About) -when did you start seeing this issue occur
Once we have this information we will be able to pass it along to the appropriate team to investigate further.