I have imported an Excel spreadsheet into a SharePoint list in 2013. There are about 20 columns. I am trying to make the main column, single line text field, (not sure if that is the correct terminology) to enforce unique values. I click to index and I get an error stating that there are duplicate entries but I have visually verified using conditional formatting and there is no duplicate entries. What am I missing?
Thank you in advance with any help.