when using Chicago style, Mendeley always cite like this " (Abrahão, Moriguchi, and Andrade 2016)", while t need to use this style "Abrahão et al., (2016)"
Check the number of authors, if 3 (or less than 6) Mendeley will not create et al. for most styles. Especially if the three authors equally contributed to the referenced paper. If necessary, you can edit manually in the Word file.