The cervix needs to be open to do a uterine flush. I can't see oxytocin working at this point. You might want to try penicillin and either lute or estrumate. Since your doe has a retained placenta, I would do a 14 day course of penicillin. But on days 4 & 5 of penicillin, give one shot of lute. So that would be 2 days in a row of lute. Hopefully that would help to expel what is in the uterus. The penicillin needs to be the twice a day type. You need a constant level of penicillin through this.