no differences but two completely different pdf.How to solve it?

[ushio20]

no word list no word list Traceback (most recent call last): File "/opt/conda/bin/pdf-diff", line 8, in sys.exit(main()) File "/opt/conda/lib/python3.6/site-packages/pdf_diff/command_line.py", line 498, in main img = render_changes(changes, style, args.result_width) File "/opt/conda/lib/python3.6/site-packages/pdf_diff/command_line.py", line 193, in render_changes raise Exception("There are no text differences.") Exception: There are no text differences.