The cancelled transactions could be 2 possible reasons. First we had a maintenance window of ~8hrs yesterday 12/22/15 where most of the Xapo infrastructure was off while we made upgrades. This has since ended and your transactions should be going as normal.

The other reason is if users are withdrawing for the first time. If a user doesnt have a Xapo account and withdraws from a service using our APIs they will receive an email inviting them to claim their bits (by creating an account with Xapo). Over a 10 day period we will send them many email reminders, but if the user does not claim the bits are returned to the service in 10 days. We set it up that way because we had many faucet partners who paid the user but many of them never claimed their bits... so at least now the funds will return to the service.