Surprisingly: USB-C cables do have an orientation. It comes up a lot with these kinds of female-to-female USB-C cable extenders: https://www.amazon.com/dp/B0CT

Surprisingly: USB-C cables do have an orientation. It comes up a lot with these kinds of female-to-female USB-C cable extenders: https://www.amazon.com/dp/B0CTT1FJL6 https://www.amazon.com/dp/B0CTT1FJL6 (I have not used this one, it's just an example) >Important Note: Ensure your USB-C cables support video transmission when using this coupler for video pass-through. If the connection doesn’t work initially, try reversing the orientation of the cable’s plug to ensure proper functionality, as USB-C protocols depend on connector orientation. AFAICT not all cables are like this, but quite a few are, and broadly it appears that it's the sockets that are reversible and are simply hiding this - cables often just use one side. So when you bridge two cables like this, you need to make sure those (unmarked) sides line up. So I suspect one side of your connection is either damaged or cheap (and didn't fully meet the reversible spec to save money). (but only suspect, I haven't found a way to fully validate this)