Due to an ongoing security issue, Score/Lilypond have been disabled on Wikimedia wikis for the time being.
This task serves as the public tracking for this issue
Multiple security issues were found in Lilypond, the software used to render musical notations in <score> tags. Some have been fixed, but others are still outstanding. The current plan is to move lilypond to a more secure, isolated environment called "Shellbox": T260330: RFC: PHP microservice for containerized shell execution. Once that's done, we plan to re-enable Score.