Originally Posted by dragon49
REplying to my initial post, as can't figure out how to edit the original. Intended to say that Amazon support told me that the original HDMI cable wasn't HDCP compatible.
First of all, there is no such thing as an "HDMI 2.1" cable. There are cables that have been tested for some of the HDMI 2.1 option sets but that's about all. Besides, it's the HDMI chipsets in the source and sink end that determine what you can ultimately receive, not the cable. The cable is just the data path. "8k" is all marketing fluff at this point in time. The same for the 48Gbps bandwidth.
How long is your cable run? Under 25' all you need is a Premium High Speed HDMI cable (passive) with the QR label of authenticity. Those cables are tested by HDMI.org to meet ALL of the HDMI 2.0 options sets, which includes HDCP 2.2. If over 25', then a hybrid fiber cable is what is recommended. Hybrid fiber cables are active so they can not be certified by HDMI.org, the same as active copper-only cables.
You mention HD. Is that 1080, 4k, or 4k HDR that you are trying to view? Amazon Prime can send 4k HDR so what are you trying to receive?
The most reliable connection is a single cable, source to sink, with no extenders, adapters, wall plates, etc in-between. USB to HDMI can be a big problem because one, I don't think USB can handle the data required for 4k and two, if the fiber optic cable from Amazon is active, active cables draw a bit of power from the sink and source end so the cable needs to be connected directly to a power source, either the HDMI input or something like a voltage inserter. 4k HDR can be very finicky with its cable connections.
Another issue could be the HDMI chipsets. While HDMI is backwards compatible, that only means that you will probably get a signal that works but the option sets available will only be the in-common option sets. In other words, if you have an HDMI 2.0 chipset (HDCP 2.2 for example) that is connected to an HDMI 1.4 chipset (HDMI 1.4 doesn't usually contain HDCP 2.2 compatibility), you will only be able to receive data that doesn't require HDCP 2.2 and unfortunately, 4k and beyond requires HDCP 2.2. HDMI 1.4 is fine for 1080p HD content but that's it.
So, it sounds like you have a two-fold problem. One, the "break" in the HDMI chain (USB to HDMI adpater) and two, different HDMI chipsets in your source and sink devices.