What is HDCP?

In plain language

High-bandwidth Digital Content Protection encrypts the video between source and display. Before protected content plays, the two sides exchange keys and confirm each other. Only then does the picture appear.

There are versions. HDCP 1.4 covers older content; HDCP 2.2 and 2.3 are required for most 4K streaming and UHD discs. Every device in the path has to support the version the content demands.

Why it matters in your setup

HDCP failures look exactly like every other HDMI failure: black screen or a rights message. The tell is that unprotected content works fine while protected content does not. A menu that displays and a film that does not is almost always HDCP.

An older switch or splitter in the chain that only speaks HDCP 1.4 will block 4K streaming even though everything else in the system is capable.

What the DR HDMI 8K does with it

The DR HDMI 8K passes HDCP through as a repeater. It does not strip or bypass protection, and it should not be expected to. Its role here is diagnostic: because it shows you that the EDID exchange and the link itself succeeded, a failure that survives all of that points squarely at HDCP rather than at the negotiation. Note that its HTPC mode is not compatible with an HDCP signal.