Looking at this page in my history one can see some listens at the top which do not display any cover art (with the tooltip: “We could not load the album artwork”).
This appears to be because the release which I had listened to (
97a8dcf7-7c3e-4ecb-9a38-18a556e50bfd) has now been deleted on MB due to a merging with a duplicate release. If this was a release deletion without any merge, seeing no artwork would make sense, but since this was a merge, and that MB retains the release MBID of releases deleted in the process of merging and redirects deleted releases to the remaining ones, I’d expect LB to still be able to fetch and display the cover art.
If that’s not the source of the issue, the problem could lie with the fact that the release has two cover arts present, both of which are Front types.