Bluray disc will not play on HDR player

[Silverage]

As the title really. I’ve got a relatively old (2009) bluray disc that my fancy new Panasonic 4K player will not touch. Claims there is a compatibility problem. It’s been fine with other non-4K discs. I tried the disc on my old standard Panasonic bluray machine and it played fine.

Firmware is up to date on the new player. Not the end of the world by any means, but I wondered if anyone has come across this before?

[legzr1]

Is it the correct region?

[Silverage]

Yes, it’s marked as a region B disk.