Is this about the TV app on your Mac? HDCP is about the video connection between decoder and screen.
- Do you try to watch it on the built-in screen? External screens could have HDCP issues, either with the cabling, screen, or adapters.
- Has your Mac video circuitry ever been broken and repaired?
- Have your tried with minimal peripherals attached, in case one of those interfere?
Else the error message itself might be erroneous. Then contact Apple Support about it. Contact Apple for support and service (phone numbers) or start your support request online (chat/email/callback).