Before trying to insert or delete a footnotes or endnotes, ensure that the document is properly formatted.
Here are some things to consider:

1. Check the page layout: Make sure headers and footers are invisible and page margins are set to 1 inch all around.
2. Check the Footnote settings: Look in the document’s Footnote or Endnote sections and make sure Footnotes or Endnotes are enabled, the bottom of page or end of document setting is chosen, and that the ‘Linked to Previous’ is disabled.
3. Check for document errors: Run the document’s spell checker and save it.
4. Restart the application: Close and re-open your word processing application.