I am writing a paper in which I cited together four articles like this : Caretto, 1970#1541;Bonfiglio, 1996 #1497;Bianucci, 1991 #1481;Bianucci, 2002 #1483.
See that there are two Bianuccis corresponding to two different years. The formated citation is, however, like this: (Caretto,1970; Bianucci and Landini, 1991; Bonfiglio et al., 1996; Bianucci and Landini,2002)
The citation shows the two articles by Bianucci separated, and they should be like: Bianucci and Landini 1991, 2002)
You don’t tell us which style you are using and whether it says the two should be combined (edit style, Citations, Author name settings. If it is - it is likely that the two references have a subtle difference in the authors and Endnote interprets them as different. To fix that, edit the records by copying one of the records authors to the other. You might have to delete them and reinsert them. It also depends on how th style orders the references. It might require that the sort is based on year order, in which case it won’t reorder them, per the journals requirements. (usually Bibliography, sort order settings, although the citation sort order could be different - it usually says “same as Bibliography”.