First, verify that you have the correct permissions to create and edit endnote and footnote separators. This will differ depending on the security settings of your organization or program.
Next, make sure that the View → Footnotes and View → Endnotes options are checked. This will allow you to add and delete separators.
Finally, if you cannot add or delete separators, uninstall and reinstall the program. This should resolve the issue.

1. Verify permissions to create and edit endnote and footnote separators.
2. Ensure View → Footnotes and View → Endnotes options are selected.
3. Uninstall and reinstall program.