Thank you for reaching out on Microsoft Q&A!
As seen in your screenshot you're missing the contents of the file. The file itself is created because you've added in the filename, which basically is enough for creating the file itself. However, without contents it's not a valid file.
You can add the contents by adding the following dynamic content to the 'Blob content' field:
items('For_each')?['contentBytes']
Please click “Accept answer” if you find this helpful. Feel free to drop additional queries in the comments below!
Kind regards,
Sonny