Oh, @Robert Donovan , this is really strange. I don't know what the "Destinations Template.csv" you are talking about is and whether the error is related to it. But I still think that if it is what you said that the file cannot be found, the error message should not be like this. At present, I can't determine which step the root cause of the problem is. Therefore, I suggest you use another migration tool —— SharePoint Migration Tool. This is also a free migration tool launched by Microsoft.
You can refer to this post to implement your migration:
https://www.sharepointdiary.com/2022/10/how-to-migrate-file-share-to-sharepoint-online.html
Non-official, just for reference.
I appreciate your patience and understanding.
I hope this information helps.
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