According to the El Corte Inglés ES terms and conditions if cashback for your order has not been added to your account with "Pending" status, you should create a corresponding request in your LetyShops account within 30 days after the purchase has been made.
Cashback is credited for purchases from Spain only.
Purchases from the Canary Islands: although there is no VAT in the Canary Islands, the technical system of El Corte Ingles is made so that cashback is still credited for the purchase amount excluding VAT.