Windows form crystal report exporttodisk error with oracle DSN

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C#

Oracle

CrystalReports

My crystal report with oracle DSN connection suddenly stopped working on production server.

When i check the DSN in ODBC and test the connection it working fine but, from my windows application while exporting report to disk it giving below error.

ODBC : ORA[12154] TNS could not resolve the  connect identifier specified ...
...Error in file (temp file path)....Unable to connect incorrect logon parameters 

Everything was working fine till last week.. there is no change in application not any update had run on the server.

only 1 thing has changes earlier i used to login to server with different user now the user has changed. is this a problem? Any user profile dependency on Report and ODBC?

What I have tried:

1) I remove the current DSN and Reconfigured the same
2) Tested connection in DSN
3) TNS ping is also ok.
4) created new user DSN and System DSN.
5) Exported crystal report manually and its working but not from c# application.