Short answer: This could be related to the selected time and/or day.
Description: You need to select a suitable time slot that's big enough for the carrier. If you select a time slot that's too small, it could result into a failed request. Make sure to try and extend the time slot and try again.
It could also be related to the day. Pickups need to be booked 48 hours in advance. If you tried to book a pickup for the next or same day, the request will most likely fail. You can try again with a later date.
If the pickup still fails after extending the time slot and selecting a later date, please reach out to our support team.