Don't Save in ODT Format
Word offers you the possibility of saving a Word file in .odt format (OpenDocument Text). In this format all fields are converted to static text. You can then no longer insert references with the Word Add-In. The same applies to files saved in .rtf format (Rich Text Format).
Your Word files need to be saved in the format .docx (not .doc) in order to use the Citavi Word Add-In.