Are you getting any error messages or confirmation message that the file has been copied to the Azure server? When you say "not readable " what does that mean? you should get a 202 status code if the copy was successful.
A few things to keep in mind:
-If the destination file exists, it will be overwritten. The destination file cannot be modified while the copy operation is in progress.
-The Copy File operation always copies the entire source blob or file; copying a range of bytes or set of blocks is not supported
-The destination file is always the same size as the source blob or file, so the value of the Content-Length header for the destination file matches that for the source blob or file.
Hope that helps.
-Grace