A fully managed end-to-end service for digitally signing code, documents, and applications. (formerly Trusted Signing)
I think it's worth asking a Microsoft moderator here if the Artifact Signing team can review this privately. Basic support won't let u open a technical ticket, and Failed doesn't tell u what went wrong.
If they offer a private message, share ur validation ID there. Ask which check failed and whether the existing request can be corrected or needs a new one. Q&A can't guarantee a review.