AWS::SimpleWorkflow::Errors::ValidationException 1 validation error detected: Value '' at 'decisions.1.member.scheduleActivityTaskDecisionAttributes.activityType.version' failed to satisfy constraint: Member must have length greater than or equal to 1

[AWS SimpleWorkflow 400 0.470025 0 retries] respond_decision_task_completed(:decisions=>[{:decision_type=>"ScheduleActivityTask",:schedule_activity_task_decision_attributes=>{:activity_id=>"Activity7",:activity_type=>{:name=>"EncodeActivity.activate!",:version=>""},:input=>"---\n- 48\n"}}],:task_token=>".....") AWS::SimpleWorkflow::Errors::ValidationException 1 validation error detected: Value '' at 'decisions.1.member.scheduleActivityTaskDecisionAttributes.activityType.version' failed to satisfy constraint: Member must have length greater than or equal to 1

みたいなログ。

Activityクラスに

activity :activate! do
    {
        version: '1.0',
        default_task_list: 'activity_task_list'
    }
end

みたいな指定するの忘れてるかも。