Hi @Aparna T ,
Welcome to Q&A forum!
I tested it and the situation is the same as yours.
This should be by design. Because I checked the file, the file already has Unique permission, that is, the result has been displayed on the file's permission. There is no value to be returned here, so the return value is null.
You can also check the file's permission interface to see if the permission setting is successful.
For your reference:
https://ludovicperrichon.com/power-automate-break-inherance-and-manage-roles-on-items-and-documents/
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Have a nice day! :-)
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