How are you deploying your custom connector? Raw class files or a .jar file? I’ve run into similar issues in the past. I would try deploying class files to classes-connectors as opposed to /classes or compile the connector classes into a JAR and deploy the JAR in the same folder where you dependencies are (/lib-connectors/GVOL). The issue is that there are separate class loaders for connectors vs other core IIQ functionality, so if your connector class is not in the right place, it cannot load your dependencies.
Topic where I asked about this before: Custom Connector, Connector Classpath, and SSB