A statement from Formula 1 read: "Following ongoing discussions with the promoter and authorities in Japan the decision has been taken by the Japanese government to cancel the race this season due to ongoing complexities of the pandemic in the country.

「日本のプロモーターおよび当局と協議を続けてきましたが、日本政府は、日本におけるパンデミックの複雑な状況を考慮して、今シーズンのレース中止を決定しました」
https://www.formula1.com/en/latest/article.formula-1-confirms-2021-japanese-grand-prix-has-been-cancelled.2Cn8r5e6lIm00IW984WnfW.html