"You have reached your account top-up limit" error when trying to redeem Fortnite gift card

To resolve this error, you must spend existing funds in the Epic Games Store to lower your balance below the limit enough to allow the gift card to be redeemed. If the amount is lower than anything available for purchase in the store, you can top up paying for something with another method of payment.

There are standard limits for an Epic account balance, but they may vary per region.

USA and Canada:
Your Epic account balance cannot exceed $500 USD ($600 CAD) or equivalent. Additionally, the total transactions to and from your Epic account balance within a 24-hour period cannot exceed $500 USD ($600 CAD) or equivalent. Furthermore, the total transactions to and from your Epic account balance within a 12-month period cannot exceed $5,000 USD or equivalent.
Note: If you are in the US or Canada and you haven't enabled Two-Factor Authentication (2FA) on your account,  the limit is $150 USD ($200 CAD). To increase the limit to $500 USD ($600 CAD), refer to Two-factor authentication (2FA) and how to enable it

Germany:
In Germany, your Epic account balance cannot exceed €250. Additionally, the total amount added to your Epic account balance within a calendar month cannot exceed €250. Furthermore, the total transactions to and from your Epic account balance within a 12-month period cannot exceed €3,000.

Mexico:
In Mexico, your Epic account balance cannot exceed  $3,500 USD or the equivalent in Mexican pesos. Additionally, the total amount added to or spent from your Epic account balance within any six-month period cannot exceed $3,500 USD or the equivalent in Mexican pesos.