I have some over-long track titles which appear as greyed-out (dimmed) text in my Sonos music library. My first thought that these tracks had been somehow lost or failed to be recognised from my NAS Drive, however, on checking these track existed

I found that you cannot select a greyed out track title to play now, but you can select the album containing the greyed out track title to play.

If the Sonos App has a limit on the number of characters for a track title, I suggest the track title should always be displayed in normal text with … following the last character, indicating the title has been truncated.