It sounds very much like the device you are trying to share is showing (or playing audio) as HDCP content.
The Room Kit endpoint will (correctly) detect that the content is protected, and prevent you from sharing it (either audio or video - it doesn't discriminate) with a remote participant. If it's protected, it cannot be transmitted.
Your solution is to use something that doesn't try to display HDCP content, or insert something in the signal path before the Room Kit endpoint to strip the HDCP from the content you are sharing.
Wayne
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