Possible reasons:
*'''Merchant Code''': The merchant code reflects your type of business (hotel, restaurant, grocery shop etc.). You can only charge a virtual card for a booking if you merchant code category (MCC) is relating to accommodation – 7011. Contact Stripe support and ask them to let set your MCC code to reflect 7011.
*'''Missing CVC''': Booking.com and Expedia do not always send a CVC for virtual cards. Ask the channel to provide a CVC for the virtual card and manually reenter it. For Expedia virtual cards you can try to add the generic CVC codes: