for a direct booking on the website when people put the discount code, we see the letters in capital letters at all times but the system is sensitive to lower and upper case letters. We often have errors because on cell phones, the first letter is always capitalized and that always creates errors. No matter what people write, it appears in capital letters. If we make a promo code in capital letters, customers write the first letter in capital letters and everything else appears in capital letters without being so, and if we make a code in lower case, people make mistakes because the first letter is in capital letters automatically. It's confusing but it's not easy to explain in writing!