It seems the path to the DOCX you are trying to use as template doesn't exist or it's not a DOCX but other file (a DOC or any other file). Please check and test the included samples with the included DOCX files. We have tested the class and it's working perfectly.
A DOCX file is a ZIP archive. If you get the following error: Error while trying to open the (base) template as a zip file , is because you are trying to open isn't a ZIP (DOCX) file.