False promise by British Airways

On 27 March I received an email from British Airways that I could request a future travel voucher for my parents who were due to travel on 1 May 2020. I then requested the voucher via the link provided. On 6 April I got a response that the booking is not eligible for the future travel voucher. How is this even possible when the airline initiated that process? I'm greatly disappointed in the manner of the process.