The information in this article can help you when:
Error code 9001-0000 is received while attempting to purchase a game or Nintendo Switch Online family membership from the official Nintendo website.
What to do:
Visit Nintendo's Network Support page and check for any posted service maintenance or outages.
Once the related maintenance has ended, try to purchase the game or membership again.
If there is no maintenance or outage posted, attempt to make the purchase at a later time.