On what screen are you trying to display? Not all displays support HDCP. Especially adapters can be a source of incompatibility.
If you didn’t tamper with the insides of the notebook, then it would always be HDCP compliant on the internal screen. However, you can’t do screen recording/screen sharing in hardware or in software while playing HDCP protected content.
Try playing without any peripherals attached.
Try playing without any other software running.
Try playing in Safe Mode.
Try playing in another Mac user account.
Else the error message itself might be in error. Then contact Apple Support for further assistance.