According to an email sent out to those affected, the cancellations are due to invalid payment options, despite many people saying their information hasn’t changed since making the initial pre-order:
Unfortunately your bank has come back to us and they have not allowed the payment to go through. For your security and privacy they do not share the reasons with us.
We do know that they usually reject payments for some of the following reasons: Billing address does not match registered card address. Sufficient funds not available. Card expired/out of date.
What this means is that we cannot collect payment or ship your order right now. Please contact Customer Service on 02088270099 and we will replace your order for you.
According to an update by Eurogamer, GAME has admitted the cancellations were caused by an ordering system error on their end. Customers who were able to contact customer service after a lengthy wait learned that GAME would be contacting people over the weekend, though GAME themselves hasn’t issued a formal statement.
So, if your order was cancelled, expect to hear from GAME in the next couple of days.