Hi @Anonymous ,
I have made a test on my side, it has the same issue with you.
I think it‘s because that when you create a excel file, the action can't identify where to store the file content(which range, which cells).
To check this issue,I have made some tests.
When I used file content from a excel file to create a excel file. The excel file can be read successful.
However, when I used the content from other types file, the excel file can't be opened as your issue.
If you want to insert the data from an azure active directory into a excel file. I am afraid you need to create a excel with a table in the SP first.
Then you can use the 'Add a row into a table' action of Excel online to insert the data into the file.
Best Regards,
Community Support Team _ Zhongys
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