Accidentally cancelling an order isn't the end of the world. The fix depends on where the order was in the process when it was cancelled.
Mark the duplicate order as 'Paid' because your customer already paid in Shopify. Don't charge them a second time.
If you cancelled an order that was never fulfilled
Head over to the 'Orders' page.
Expand the order in question by clicking on it.
Click the 'Undo Cancellation' button.
If the order was cancelled during processing
Head over to your Shopify backend.
Find the order in question then click on it.
Click the 'More Actions' dropdown.
Click the 'Duplicate' option.
Add the correct customer.
Click the 'Collect Payment' button.
Click the 'Mark as Paid' button.
Click the 'Create Order' button.
Head back to Zendrop and refresh to see the duplicated order.
Go to the Orders page in your Zendrop dashboard to check your current order statuses and act quickly if needed.