3x Argon ONE M.2 ... on all HDMI is not working!

Dear Argon-Team,
I’m owning now three Argon One M.2 Cases.
I had some issues with my systems and want to connect an external display via HDMI.
On all three Cases I cannot get any external HDMI to work! When I take out the RPI4 it’s working fine, without any problems, inside the Cases not.
Have I forgot something? Missed something? Can you give me helpfull advices?
Thank you, greets from Germany,
Ralf aka synth

You ARE using the correct HDMI socket ?

  • HDMI_0 is nearer the case edge,
  • HDMI_1 is nearer the 3.5mm audio socket.

Yesterday evening I found out that it might be a problem with/between display & case.
Ordered another display and now it’s working fine.
Finally no idea what’s the “real” reason.