Steps to replicate the issue (include links if applicable):

• Go to https://da.wikipedia.org/wiki/Harpe
• Press the |> button to play the score/lilypond

What happens?:
The window is greyed out. No audio is produced.

What should have happened instead?:
The music should play.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):
The same music is on this page: https://da.wikipedia.org/wiki/Arpeggio and there it will play.

Another piece that will not play is this one: https://da.wikipedia.org/wiki/P%C3%A5skeblomst!_hvad_vil_du_her#Musik This has previously worked.

Downloading the MIDI file works.

Note part of the interface for those scores/Lilyponds that do not work is missing: the slider, the timing information and the loudness control. Only the triangular button is there.

I have tried to refresh the cache, use another browser: Firefox, Chromium, Edge on Linux. They all exhibit the problem.