Disha,
PFB my replies on your questions.
1. Regarding Rejection reasons- I don't think it is anyway related to GATP, I think line items are rejected manually by someone and hence are not getting picked BOP. Is the issue happening for every run of BOP? Have you tried creating a New Order and tried running BOP on that?
2. Yes there is setting in BOP for not taking confirmation away from already confirmed Orders.
