Volume issue with Max Richter's Sleep

I have the flac version of Max Richter’s Sleep on my plex server, but it’s extremely quiet on all of my devices with either plex or plexamp. I initially thought there was no sound at all, but it’s just quiet to the point of inaudible, only starts to become audible when I turn the volume up to about 80% on my device. The normal listening volume for other songs would be somewhere around 25%. Haven’t experienced this issue with any other album so far

Probably loudness leveling.

I have tried toggling it on and off to no perceivable effect. Is there anything else I can try?

Are you sure the file wasn’t encoded at low volume? Have you played it with some other player?

Yup, directly playing the file on a number of different device all work perfectly fine

You need to stop and restart playback after toggling.

I’d check all tracks for blips and other (possibly very short) signs of data damage.
Even if you have only one damaged track, this can offset the loudness detection and make all tracks of the album play at the wrong loudness level.