Is that the message you’re getting, or does your tv not support HDCP?
If it’s the message, try calling your TV manufacturer to see if the HDCP compliant device within the TV is functioning correctly.
HDCP is a form of copyright protection and there are various versions. If you are trying to get an HD (4k) video the sending unit, Hopper or other player, will be using a newer (probably V2.2) version to protect the content, if the receiving TV does not support the newer version (v 2.2) the sending device will,not send out the video. If you are watching a 1080 or lower resolution video the Player will send the picture to a TV even though it has an older version of HDCP.
It's a never ending mess. Some hackers have already been able to hack HDCP 2.2 so they recently released HDCP v 2.3. I am not sure how it will be implemented or what problems this will cause but I'll bet that eventually there will be some innocent people who will be unable to watch some content because of it.
The last thing to check is if your player (Hopper etc) is wired directly to the TV, if it first goes through another device (audio system etc) then to the TV that may produce the HDCP problem as well. Try wiring it directly to the TV.