This error message typically appears when there is a conflict between the citation styles used in your document and the Mendeley software. Here are some steps you can take to resolve the issue:

✓ Check the citation style: Make sure that the citation style used in your document matches the style in Mendeley. If there is a discrepancy between the styles, it may cause the error message to appear.

✓ Remove the index area: If the error message persists, try removing the index area from your document. To do this, go to the "References" tab in Word and click on "Insert Index". In the dialog box that appears, select the "Index" tab and click on "Delete Index". This should remove any existing index areas in your document.

✓ Re-insert citations: Once the index area has been removed, try inserting your citations from Mendeley again. Make sure that the citations are placed in the correct location in your document and that they are formatted correctly.

Regards,