Superb @Gentlecat, thanks very much, now I can see a detailed error message !
Cannot add this dataset because of a validation error: Can't find
low-level data for recording: 0091e4e9-e521-4ef9-8085-61960bb2b156
I should probably start by submitting an AcoustID…
EDIT: It could be helpful that the plain text MBID would rather be a link — here, 0091e4e9-e521-4ef9-8085-61960bb2b156.
EDIT2: Sorry, I confused AcousticBrainz and AcoustID.