Is the external data source a FileMaker database too? If so, there are two things to check:
A) does the authenticating account exist in both the front-end database, as well as your external data source?
B) is WebDirect enabled on both the front end file, as well as the external source? (see File menu --> Sharing --> Configure for FileMaker WebDirect...)
If either one of those conditions is not met, the WebDirect session of the front end file is not authorized to access data from the external data source.
If you don't want users to see the external data source in the WebDirect start page, check "Don't display in WebDirect Launch Center".
Yes, they are both FileMaker Databases on the same FileMaker Server.
A) Yes, the account exists in both databases.
B) Yes, WebDirect is enabled on both databases.
I use to have this database on the web when using FileMaker 11 Instant Web Publishing and it worked fine, just need to fix this one field that is coming from the external source.
Thanks for your reply!
The last thing that comes to (my) mind: is the WebDirect session truly logged-in with an account that exists in both files?