If you are getting an error with the discount code, it might be because of this.
View Automatically Issued Discounts
Open the Ryd App main menu by tapping on the β° on the top left.
Then tap on My profile
Scroll down until you see Discount Code Manager
Tap this, and you will see any discounts loaded to your account.
Redeem a Discount Code
Open the Ryd App and select the desired vehicle. Tap on Book now to create the booking
Tap on Redeem discount code, to get to your Discount Code Manager
Select an existing discount code or add a new discount code by tapping on the β+β symbol