can't update drop down field from excel plug-in

I am using Sugar Professional 6.5.16. The excel plug-in seems to be working fine for updating regular text fields. However, when I update a field in excel with a value from a drop-down table, it doesn't update. I don't get an error message when I update in excel, but when I go to the CRM on the web I don't see my update. Suggestions are greatly appreciated. Thank you.