Your task definition contains a parameter that requires a specific container instance attribute that is not available on your container instances. For example, if your task uses the awsvpc network mode, but there are no instances in your specified subnets with the ecs.capability.task-eni attribute. For more information about which attributes are required for specific task definition parameters and agent configuration variables, see Task Definition Parameters and Amazon ECS Container Agent Configuration.

bind-key -n C-S-Left swap-window -t -1
bind-key -n C-S-Right swap-window -t +1

Pressing Ctrl+Shift+Left (will move the current window to the left. Similarly right. No need to use the modifier (C-b).