Vouchers can only be redeemed on the same Nintendo Account that purchased them.
Nintendo Switch Game Vouchers can only be redeemed on a Nintendo Account with an active Nintendo Switch Online membership that is not a free trial.
Vouchers can only be redeemed in the same region where they were purchased.
What To Do
Close the Nintendo eShop and log back in using the Nintendo Account that purchased the set of vouchers, then try to redeem a voucher again.
Review your Nintendo eShop Purchase History to verify that your Nintendo Switch Game Vouchers haven’t already expired or been used.
Vouchers expire one year after their date of purchase.
Visit the Nintendo Accounts website, and sign in to your Nintendo Account.
From the profile settings, select “Shop menu.”
Select “Purchase History.”
A list of the transactions associated to your Nintendo Account will appear here, as well as any promotional or bundled download codes included with your purchases.
Verify that you still have an active, paid Nintendo Switch Online membership.
Make sure your Nintendo Account country settings match the region you used when the vouchers were purchased.
Check the list of games available to purchase with a voucher to confirm that the title you wish to purchase is eligible.
Confirm that the game has not already been purchased on your Nintendo Switch console.
If a title is listed as “Purchased”, it can be redownloaded at no cost using the Nintendo Account that bought it.
Situation Not Resolved
If the issue persists, please contact Nintendo Consumer Support.