Which player do you use to play on?
You might be using one of the old players which are being phased out such as MACOS player or PC player and will play transcoded in SDR and not DoVi.
Sorry to bring this bad news to you.
I can guarantee you that it is not playing in Dolby Vision in the new players as per Plex support which stated very clearly that they will not support a non compliant implementation such as this one.
So when the old players are phased out which is happening one by one slowly in 2025, these movies will not work at all and you will get an error message on the player saying that this can not be played, just that you are aware.
This will not play in DoVi in Infuse, emby, VLC, Sony TV, Samsung TV, etc...
All these have been tested and will not work in Dolby Vision, some might play in SDR, some might just not play anything bringing up an error message...
I spent a lot of time with Plex support and other player support to convince them to support this non standard implementation and all of them just refused to do so, now the ball is in the UniFab/DVDFab camp to fix it.
