Failed when run code deploy

Hi AWS team, I am trying to run "AWSCodeBuild" but am getting below error. I did some research and the result is "Concurrently running builds" I don't know what "Concurrently running builds" is? What do I need to do to solve the problem.

This is error when run : Action execution failed Error calling startBuild: Cannot have more than 0 builds in queue for the account (Service: AWSCodeBuild; Status Code: 400; Error Code: AccountLimitExceededException; Request ID: 708ea06f-996c-4947-b907-93e714ac25bc; Proxy: null)