When you place an order, it goes through an Uploading step where your files are processed and prepared for production. Normally, this only takes a few minutes.
If your order has been stuck in Uploading for more than 15 minutes, this may indicate a temporary issue in the backend at the time the order was placed.
What you can do
To resolve this issue:
Cancel the order that is stuck in "Uploading."
Place the order again. In most cases, this clears the error and the order proceeds normally.