If you see a blue led flashing during start up, that means the RT2xPro enters a DVI mode (no audio), because your monitor reports DVI only.
The RT2xPro is default to HDMI mode (with audio), and it’s very unusual that a monitor reports DVI only if it is HDMI compatible.
The RT2xPro double checks that EDID has been read correctly and then checks for HDMI compliance,, if anything goes wrong, it will default to HDMI with audio.
Try to plug the power first, then plug the HDMI cable.
What is your TV, Monitor, or other display?
How long is you ‘cable management’ now?
Also, do not flash the firmware endlessly, only once is enough if it was successful.