Bonnie,

From workflow designer , the activity to query external database will use ODBC connection information to connect to the third party database. If you are using windows authentication, that means when you test the activity through the workflow designer, it will use the current windows credentials. But when it runs through workflow it will use the workflow credentials assigned to the workflow server service.

I do recommend to check under Services, as to what account is running the workflow server services and confirm it is running with an account that has the necessary access rights to query the database in question. In case it is running with an account that should have access rights but still not working, I suggest to review the Workflow Logs files which are located in your Logs folder under your workflow installation, typically  C:\Program Files\Laserfiche\Laserfiche Workflow\Logs.  Please contact your reseller who can open a case with Laserfiche Technical Support , the logs files should be attached to the case.