Airflow tasks are staying in queue

I have observed that only 18 maximum tasks can run in parrallel any other task remains in queue and i think wait for the other task to finish.

I have set the Environment Variables of Astronomer with 64 tasks concurrency but still no luck. Can someone guide which are more properties can be set and what about the resources If I increase scheduler count and CPU, will it be helpful for not.

@Alan Ma Can you please look into that