Hi Karthi,
In the IMG, please check the setting for "Release Time" in the Activity Sequence for Export. From what you say, I expect that your system is set for "No Release"; if so, that's the reason for your issue. Make sure that you set the Release Time to 'A' (creation of an Customs Declaration).
If that is the reason, then we'll need to find a way to resolve the stock problem. But first, please confirm.
Regards,
Dave