Dear,
You need to check the log ECC SLG1 and CFG1 in APO please check /SAPAPO/CPP,
Couple of checks,
Active Integration Model for production orders in R/3 .
Distribution definition (T.Code /sapapo/cp1) in APO
Also try to convert the order in ECC and check are you getting any error also check Log ON Release in production order it self.
Regards,
R.Brahmankar