Please select an appropriate Pay group assigned to the operating unit error

 Hello All , 

I just created  new pay group under purchasing lookup options  and  assigned to the supplier at supplier site level . 

when I am creating a new invoice against this pay group ,  its is populating an error message saying that Please select an appropriate pay group assigned to this operating unit. 

As result I am unable to complete creation of invoice. 

Any inputs Suggested ? Appreciate it !

Thanks, 

Deepthi.