So you imported the contact information from Excel files? best guess is that you ran afoul of a common user mistake that really, really should be documented inside the starter solutions to help new users avoid this one. Best guess is that you didn't click the check box to enable auto-enter options during import and thus all your imported records lack the needed value in an ID field.
Here's an old thread dealing with the same issue in another file and version of FileMaker. The options for correcting the issue, however will apply to your file if I am right as to the cause of your issue: Help importing Excel data into a Filemaker Starter solution
Thank you very much. I got it to work.