Once you have printed the allotted number of copies and confirmed that they printed successfully, you cannot print a piece of music again. Each printed copy of an ePrint sheet music purchase is a purchased copy, just like a traditional copy printed by the publisher. If, for some reason, you lost a traditional copy, you would need to purchase it again to replace it. The same is true for ePrint.
You can always view your purchased ePrint music through your online account and/or by using the ePrintGo app.