Hi Swagata R. I suspect the answer to your question is another question... "When is a csv file NOT a csv file?" The answer to which is... "When it's not been created by Workato!"
I wonder if you've made the same assumption I did, that uploading a valid csv file to FileStorage should just trigger the Recipe and process the file (and why wouldn't you?). Except that if Workato did not create the csv, it won't be able to read it. I guess it needs to have pre-parsed the file to know the column structure?
What I did in my Recipe was to invoke the "Create File" action first, passing in the contents from the file that triggered the Recipe, and then ensuring you choose Yes for the "Create CSV" file option.
Once you've done that you can use the output from that Step in the Recipe (rather than using the Trigger data). See screengrab for a sample.
I hope I'm wrong and this is unnecessary and I'm missing something. But this worked for me. (Waits for gary to come along, point, laugh, and school us in the Way of Worakto...).
Cheers
Russell