@Rob N
Please try attaching a SAS token with appropriate permissions to the copy source url. There is a recent GitHub thread where a user faced the same issue. Here is the code that worked for them:
String sasToken = sourceBlobClient.generateSasToken();
copyBlobClient.copyFromUrl(sourceBlobClient.getBlobUrl() + "?" + sasToken);
Hope this helps. Let us know if you need further assistance or have further issues.
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