CXone Studio DBConnector returning empty result set for valid query

Trying to pull customer data in a CXone Studio script using the DBConnector action. The query works fine in our SQL client, but returns an empty set in Studio.

Query: SELECT * FROM users WHERE id = {{vars.userId}}

The connection profile is active and I’ve verified the credentials. Is there a specific syntax for parameter binding in the DBConnector action? I’m getting no errors, just empty results.