Error Searching Duplicates

I have a library that I have had for a long time through various versions of EndNote and it has about 2500 references. It has a number of duplicate references in it but when I try to review these, the duplicate function does not work. I get an error message that states “this is not defined” (see attached screenshot). I have gone into the Endnote preferences to make sure I have set the parameters for the duplicate search and these are set. The find duplicates option works fine in my other libraries. I have tried to copy and import all of the references into a new library and once I do that, I get the same error message.