No cover art appearing at all

Am using Windows 10 & Firefox Nightly.

Initially thought this was temporary but it seems permanent. eg.

https://musicbrainz.org/release/61b643cc-1d77-4056-8851-dc17c667c6a4 gives me Front cover image failed to load correctly.
View all artwork. Clicking on the latter shows image placeholder(s) that all say Image not available yet, please try again in a few minutes.

After a few minutes, hours or days the result is the same_._ However noone else seems to be up in arms about it, so it must be me! Perhaps am the only one using Firefox...