I have tested your scenario/ case a bit using the following sample code and it works fine. I am using latest version of the product. I have also attached the header image file and output Excel file for your reference.
//Instantiating a Workbook object
Workbook workbook = new Workbook();
//Get First Worksheet of the Workbook
Worksheet ws = workbook.Worksheets;
//Creating a string variable to store the url of the logo/picture
string logo_url = “e:\test\school.jpg”;
//Declaring a FileStream object
//Declaring a byte array
//Creating the instance of the FileStream object to open the logo/picture in the stream
inFile = new System.IO.FileStream(logo_url, System.IO.FileMode.Open, System.IO.FileAccess.Read);
//Instantiating the byte array of FileStream object’s size
binaryData = new Byte[inFile.Length];
//Reads a block of bytes from the stream and writes data in a given buffer of byte array.
long bytesRead = inFile.Read(binaryData, 0, (int)inFile.Length);
//Creating a PageSetup object to get the page settings of the first worksheet of the workbook
PageSetup pageSetup = workbook.Worksheets.PageSetup;
//Setting the logo/picture in the central section of the page header
//Setting the script for the logo/picture
//Setting the Sheet’s name in the right section of the page header with the script
//Save the workbook
Could you try the above code with your header image (please set the path for the image file and output Excel file accordingly). If you still find the issue with latest version, kindly attached your image file here, we will check it soon.