My Voucher

I received red letter days voucher on the 20th October 2023 which expired on the 20th October 2024. I redeemed my voucher on 4th October 2024 which then said I have up until 19th of November 2025 to use the voucher. Now I'm trying to book the venue, but when doing so it says the voucher is invalid. Can someone from red letter help me please.