This error can be caused by using different Dante AV firmware versions on TX and RX units. Between Dante versions 4.3.10.x and 4.3.11.x, the network HDCP implementation changed. V4.3.11.x or later is not backwards compatible with previous Dante AV Ultra firmware versions.
Open HDCP error.png
To solve this issue, all Dante AV Ultra units must be running the same firmware version. It is recommended to update all units to the latest Dante AV Ultra firmware version.