External task client for plain Spring NOT WORKING

@Configuration
@EnableExternalTaskClient(baseUrl = "http://localhost:8080/engine-rest")
public class SimpleConfiguration {
}

Can somebody explain to me, why this not working?

Caused by: org.camunda.bpm.client.exception.ExternalTaskClientException: TASK/CLIENT-01001 Base URL cannot be null or an empty string

and why this check present in lib?

> Predicate<String> isClassAnnotation(ListableBeanFactory listableBeanFactory) {
>     return (beanName) -> {
>       return ((BeanDefinitionRegistry)listableBeanFactory).getBeanDefinition(beanName).getSource() == null;
>     };
>   }

Hi Is it possible to change a property of camunda json variable via rest api? I know how to change variable itself, but the problem is when you try to change one object from several parallel tasks - the last modification erases other interactions…