If your Switch eShop gift card isn’t working, start by checking the code. Ensure you entered the code correctly—look for similar characters (e.g., 'O' vs '0', 'I' vs '1') and type slowly. Check if the gift card is for the correct region—eShop gift cards are region-locked (e.g., a US gift card won’t work on a European eShop). Verify the card’s balance: go to the eShop, select your user profile, and check 'Account Information' > 'Funds' to see if the balance was added. If the code is unreadable, contact the retailer where you purchased the card for a replacement. If the card is valid but still not working, contact Nintendo Support—provide the card’s serial number and purchase receipt, and they can assist with adding the funds to your account. Avoid buying gift cards from unauthorized sellers, as they may be fraudulent.