Make sure you already have @EnableAsync in your @configuration file

   @Configuration
    @EnableAsync
    public class AsyncConfig implements AsyncConfigurer {
    
      @Override
      @Bean
      public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(3);
        executor.setMaxPoolSize(9);
        executor.setQueueCapacity(50);
        executor.setThreadNamePrefix("MyExecutor-");
        executor.initialize();
        return executor;
      }

here some references about it

https://www.baeldung.com/spring-async