python xlrd unsupported format, or corrupt file.
You say:
The file doesn't seem to be corrupted or of a different format.
However as the error message says, the first 8 bytes of the file are '<table r' ... that is definitely not Excel .xls format. Open it with a text editor (e.g. Notepad) that won't take any notice of the (incorrect) .xls extension and see for yourself.