That page isn’t a 404, it’s returning a status code 200. The title and body tags also indicate that the page is loading just fine.
A couple of things- there is no taxonomy argument. It would be redundant anyway, since the query already contains the queried taxonomy and term pulled from the parsed URL.
Your possible issue is outlined in this note from the WP_Query Codex page under type parameters:
'attachment'– an attachment. Whilst the defaultWP_Querypost_statusis'publish', attachments have a defaultpost_statusof'inherit'. This means no attachments will be returned unless you also explicitly setpost_statusto'inherit'or'any'.