Hi Sandy P:
Thanks for posting.
External authentication is only possible using FileMaker Server. FileMaker Pro sharing is unable to use External Authentication.
For External Authentication to work correctly, the database must first be showing as normal under the databases section in your admin console. FileMaker and External Server accounts must then be selected under the security tab in the admin console. Since some of your databases are not hosted by the server, those files cannot use External authentication. You will need to upload these databases if you want them to use authentication.