Add the following class to META-INF/services/javax.enterprise.inject.spi.Extension file.

WeblogicActivitiExtension

/**
 * Weblogic ClassLoader on CDI Extension don´t localize META-INF/services necessary to load ProcessEngine.
 * <p>
 *     This class provides an overriding extension point which uses the correct classloader, in order to instantiate
 *     a {@link org.activiti.cdi.spi.ProcessEngineLookup}
 * </p>
 */
public class WeblogicActivitiExtension extends ActivitiExtension {

    public void beforeBeanDiscovery(@Observes final BeforeBeanDiscovery event) {
        super.beforeBeanDiscovery(event);
        Thread.currentThread().setContextClassLoader(this.getClass().getClassLoader());
    }

}