One of the Approver is coming again and again even he approved the requisition

HI All ,

I have created an requisition ,using AME it has created the approval list .

but one approver is coming again and again means the first time he approves it and went to the next approver .

The next approver is approved and again it is going back to the first person who already approved it .

Oracle Apps : 11.5.10.2

Example :  

Let us assume my req created approval list as A , B ,C . This is the list shown when I have created the requisition .

Problem in the Approval Sequence :--

1.  A has Approved the req . The notification went to B .

2.  B has Approved the req and the notification went to A again.