Data not uploading in ELM

Hi Gurus,

In WebUI for ELM data upload I am following the following steps:

1> Creating a Mapping Format.(Its executing correctly)

2> Creating External List. Here is the problem I am facing after I start uploading. I am uplading.txt file with two fields only(email id and ISO country code) It is showing an error. Not able to upload data.

In dev system the process is executing correctly but in Prod its the problem.

Regards,

Roy