Hi I have EOS R6 and I am connecting the camera to Blackmagic AETM mini via Micro HDMI to HDMI connection for live training sessions, the camera outputs signal when connected via 3-5m cable but no signal when using 10-15m cables or even powered HDMI extenders.
Welcome to the forums.
You do not have a camera problem. You have an HDMI cable issue. The fact that the camera output seems to with 3-5 meter long cables means the camera HDMI works as designed.
Your problem is that the laws of physics are not working in your favor. For complex electronic reasons that are off-topic, the length of HDMI cabling has a maximum limit, 25 feet or 7.6 meters. A passive cable that is 10 meters or longer should never work properly.
If your active HDMI cable extension is not working, then you could have a grounding problem or bad gear. You have already stated that the camera works,, just as it should.
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