Hi Pankaj,
1. In your test run mode (do not tick the 'Create Posting' and fill any text in 'Batch input session name'), can see the valuation result?
2. In you OBA1, The valuation section must be filled with your forex GL account
3. If all above condition already met but still not posted, check the batch input session (tcode SM35). If there is a forex session there (usually the name of forex session is 'SAPF100'), means there is something error so it can not automatically posted. You need to check the batch input session / run it n foreground so you can identify in which field the error occur.
Regards,
Handy