There are many possible reasons for a credit card not being accepted:
For both physical products and software, sales tax will be calculated dependent upon your billing and/or shipping address.
You cannot change your shipping address after you submit your order. Orders with physical shipments are immediately sent to the Acer fulfillment facility when they are submitted and the system can no longer retrieve or change them. If your shipment is not successfully delivered it will be returned to the fulfillment warehouse and a credit will be made to your account.
It may take 1-2 business days to process an order. If you have an account set up with Acer Store, you can look up your order and see the shipping status from your account.
You will receive a confirmation email with shipping tracking number included.