Hi Abhishek
I'm asking for the third time for a screenshot of the audit/message log. Without this, it is a bit hard to imagine what happened during runtime processing in the channel.
From the incomplete information that you have provided, I can roughly guess that the swap and Excel conversion was completed successfully. Note that the Excel converter converts the content of the payload/attachment but does not change the filename. As such, that's the reason why it still prompts you to download as .xslx although the actual content is in XML when viewed in a text editor. Changing the filename is a different issue altogether since it does not affect processing in PI.
Your main issue seems to be caused by mapping failure. My suggestion is you take the downloaded XML content and test it out in ESR message mapping test functionality. The mapping may fail due to a lot of different reasons, but my first guess would be a mismatch between the converted XML versus the defined DT/MT used in the mapping. Check for typo errors or differences in namespace.
Regards
Eng Swee