Hi
For this issue reasons are
1. If you maintain the payment block at Payment terms level ,system automatically will pick up payment block while running the F110
2. If you maintain the payment block at vendor master and invoice level ,system automatically will pick up payment block Please check above areas.. You can see the payment block.
the above settings may be maintain the as per business process.
Due to that reasons you need the remove the payment block two times
1. At document level through FB02
2. While running the F110 at edit proposal level.
Then only you able to run.
hope it will helps.
Regards
Sudharsana