“When I reprinted an Invoice, the Payment that was originally on there is no longer showing.  What happened to it?”

In some instances a portion of the payment may have been applied to a different Matter or Matters.  You may have also only partially applied the payment or not applied it at all and posted it as a partially applied transaction.  At this point, Orion would have created a Retainer Balance so check Matter Status to see if there is a Retainer Balance for the Client-Matter.  The payment may also have been reversed since the Invoice was originally printed.