Could you please check the following:
1) If application listener is running
2) Check the contents of tnsnames.ora for appropriate entries.
Would advise you to compare the tnsnames.ora in the 10.1.2 ORACLE_HOME of Run FS in PROD & PREPROD.
Looks like the issue is w.r.t FNDFS to me.
Additionally, please refer:
Troubleshooting the "Error Occurred While Attempting to Establish an Applications File Server Connection" (Doc ID 117012.1)
Probably, you could try running AutoConfig to check if that resolves the issue.