I was on the Japanese wikipedia article ja:星に願いを。 and clicked the grey button on the left sidebar, to translate the article into Cantonese. The content translation tool displayed ⧼cx-error-page-not-found⧽ on top and could not load any Japanese contents, hence failing to translate.
An unrelated query. I asked a few days ago but received no attention, about defaulting non-Mandarin Chinese languages to Mandarin in the content translation tool before they are supported. Please see Topic:Ufql499r14wh9xre .