Hi Asitabha,
Once you close instance for one workbook, before opening another new workbook (i.e., in your case before 'New WorkBook') you need to create a new instance for that new workbook. As there is no active instance in your flow before New workbook action block, code stage thrown an exception. Refer screenshot.
This will work.
Regards,
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Yeswa Vaibhav Alwar Nerella
Associate Consultant
Capgemini
Asia/Kolkata
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