service [ECS_SERVICE] was unable to place a task. Reason: You’ve reached the limit on the number of vCPUs you can run concurrently. For more information, see the Troubleshooting section

Hello.

If you are using ECS ​​Fargate on-demand, try increasing the "Fargate On-Demand vCPU resource count" quota as described in the documentation below.
https://docs.aws.amazon.com/AmazonECS/latest/developerguide/service-quotas.html#service-quotas-fargate

The number of tasks that ECS Fargate can launch varies depending on the vCPU set in your AWS account.
https://aws.amazon.com/jp/blogs/containers/migrating-fargate-service-quotas-to-vcpu-based-quotas/

Service quotas can be increased by following the steps in the document below.
Also, when applying, please change the management console to the region where ECS is running and then apply.
https://docs.aws.amazon.com/servicequotas/latest/userguide/request-quota-increase.html#quota-console-increase