Unable to Break Links to External Sources

I get a message to update (or not) links whenever I open my workbook. I have deleted all references to external data and I have no validation rules. I found an older post from 2014 when the user solved the issue by removing cell validations however I do not have any cell validations that I can find. I then opened the source file and removed the connections there as well and then I went so far as to delete the source file because I don't need or want them linked. I still cannot get the link broken. Can anyone help?

Under Data on the Ribbon, check both Connections and Edit Links. Under Formulas>Show Formulas check cells on worksheet to see if any have references to sheets in other workbooks. If you have done all that, I don't know where else to look. Maybe named ranges?