If the user noticed this error in Fargate Service Events tab:

You've reached the limit on the number of tasks you can run concurrently

Solution:

• In the same Region, go to the Services search box, and search for EC2
• In EC2, start a new instance

• Choose the smallest instance size
• Once the instance is created, tear it down
• Deploy your application again

This AWS official response:

You must activate the Region in which you want to run Fargate by launching an EC2 instance in that Region. Otherwise, you will experience a Fargate concurrent task limit issue. Launching an instance will enable you to run multiple concurrent Fargate tasks.