Thanks for the template file and details.
After an initial test, I am able to observe the issue as you mentioned by using the following sample code with your template file. I found Workbook.hasExernalLinks() returns false where as it should return true as there is a DDE link in the spreadsheet:
Workbook book = new Workbook("f:\\files\\0_dde.xlsx");
System.out.println(book.hasExernalLinks()); // false
System.out.println(book.getWorksheets().getExternalLinks().getCount()); // 1
I have logged a ticket with an id “CELLSJAVA-42836” for your issue. We will look into it soon.
Once we have an update on it, we will let you know here.