DBConnector returning empty result set despite valid SQL in Studio

Running a simple SELECT query in a CXone Studio script via the DBConnector action, but the output variable stays empty. The connection string is valid and tested in a separate environment, so it’s not a permissions issue. The SQL is straightforward: SELECT customer_id FROM users WHERE email = '${system.guest.email}'. I’ve confirmed the email variable contains a value at this step by logging it. The connector action returns a success status, yet the result field is null.

Here’s the JSON mapping for the connector:

{
 "action": "DBConnector",
 "connectionName": "ProdSQL",
 "query": "SELECT customer_id FROM users WHERE email = '${system.guest.email}'",
 "outputVar": "dbResult"
}

Checked the Studio logs, no errors thrown. Just empty data. Is there a specific format required for the output variable when dealing with single column results, or am I missing a configuration step in the connector setup?