Two versions of Office are installed on your computer. Citavi installs the Add-In only in the version that is set in Windows as the default program for opening Word documents. When you use the other version of Word, the Add-In will not appear.
Solution
  1. In Windows Explorer, right-click a Word document.
  2. Select Open with > Choose default program.
  3. Select the Word version in which you want to use the Word Add-In.
  4. Switch to the Control Panel and click Programs > Programs and Features. Select Citavi [Version number] and then click Change. Click Next and then click Repair.