Blu ray/4k player not working

Interesting, was your 4K Blu Ray player working as well before?

You realise it has a 4k blu-ray drive? This is the main reason I'm getting one, it's about half the price of 4k blu-ray players in the UK.

I'm having the same issue and I tried the above "fix" to no avail. After getting the message, the Blu-ray player loads the 4k Blu Ray in 1080 not 4K. I can play it in 1080 but not 4K

Yes, 4K HDR Dolby Vision works with the Blu-Ray player and NetFlix on the Xbox One X.

The Blu-rays that say Mastered in 4K will have a better overall picture than those that aren't. I don't see that they cost anymore, at least from Amazon. Sony previously did this with a line of pristine masters of DVD's some years ago. Here is the marketing
speak:

The Blu-ray “Mastered in 4K” collection will set a new standard for Blu-ray HD picture and sound, creating the ultimate 1080p home entertainment experience. Created from the highest quality 4K source materials with new expanded color*, consumers can enjoy
a brilliant picture with exquisite detail using their existing Blu-ray player or PlayStation®3. The Blu-ray “Mastered in 4K” collection is optimized so that 4K Ultra HD TV owners can take full advantage of the new 4K upscaling technology, delivering an outstanding
near-4K experience. “Mastered in 4K” Blu-rays also work with all 1080p HDTVs for spectacular high definition picture and sound.

*Expanded color requires xvYCC-compatible TV and Blu-ray player

Why “Mastered in 4K” Blu-ray?

• Get the best Blu-ray picture possible, mastered from 4K source materials

• Push your TV to the limit with a high bitrate digital transfer for an immersive visual experience

• Ideal solution for new 4K TV owners and great for Blu-ray collectors

Notice the "near 4K" phrase? In any case they should look better when played back on equipment that will utilize the high bitrate of the disc.