When the status of your order is On Hold it means that funds have not yet been withdrawn from your Store Wallet or you have set up the On Hold time on your Store Wallet page.
Now, this also means that the order has not been paid by your customer and you have insufficient funds in your Store Wallet.
So, for all these cases, we have set up an auto-cancelation feature. This means that unpaid orders will be canceled after 72 hours.
If you hover your mouse over the ON HOLD status you will see a message like the one below notifying you that your order will be auto-canceled if it won't be paid until a specific date.