EE tv pro box not connecting to new tv and HDMI

[ABWN]

Im having some trouble connecting my pro box to my new 2025 Sasmung QLED TV. I bought a new ultra speed HDMI 2.1 and had it all mounted and cables hidden. But the tv, most of the time does not find the signal from the pro box. There have been times when it has connected, but this is very random (perhaps 10% of tries when ive made slight adjustments to the HDMI at the back of the box) Ive changed the resolution on the box using the standrd HDMI inc with the box to 720p 1080 etc but this doesnt seem to work either.

Ive done all the usual stuff, swapped different ports and resolutions, tried the new HDMI with a PS4 and laptop and that all works fine. EE even sent a replacement pro box, and still the same issue.

Is the issue that the new HDMI is having trouble speaking to the box?

Any thoughts or advice is greatly appreciated 

TIA

[lufc87]

I have my pro box connected with a HDMI 2.1 cable to a Samsung S90C (2023) and everything works fine so I doubt there is any kind of compatibility issue.

How do you normally switch everything on? TV first and then box or just with power for box?

If you have changed the resolution, proved the cable to be fine and replaced the box the only setting I can think to check is HDMI CEC on the TV. On my TV its Settings > General > External device manager.

[ABWN]

Thanks for the feedback. If i fiddle about witj the connection in to the pro box, it seems to work which is weird.