Invoice reflected at GSTR-2A But Not Reflected at GSTR-2B

Our Supplier uploaded his Invoice at GSTR-1 on 9/12/21 for the Period of Nov'21

Accordingly Said Invoice is Reflected at Our GSTR-2A  for the Period  of Nov'21

But Said Invoice Not Reflected at our GSTR-2B for the Period of Nov and Dec 21 Both

( GSTR-2B for Dec ' 21 already Generated)

I don't Understand why this behaviour at GSTR-2B 

Please reply ... thanks