Function "SaveSlotDetails" does not presented in serverless.yml

Question

I am using npm package https://www.npmjs.com/package/serverless-step-functions-offline for running step functions offline. However I get the output form serverless as

Function "SaveSlotDetails" does not presented in serverless.yml

I have follwed the steps exactly as per the documentation, but I am not able to run the step function locally

Below is my serverless.yml file content for the related context

custom:  
  stepFunctionsOffline:
    SaveSlotDetails:CreateSubscription

functions: # add 4 functions for CRUD
  createSubscription:
    handler: handlers/subscriptions.create
    name: CreateSubscription
    events:
      - http:
          path: subscriptions # path will be domain.name.com/dev/subscriptions
          method: post
          cors: true

stepFunctions:
  stateMachines:
    SlotCheckingMachine:
      name: ProcessSlotAvailabilityStateMachine
      definition:
        StartAt: SaveSlotDetails
        TimeoutSeconds: 3600
        States:
          SaveSlotDetails:
            Type: Task
            Resource: "arn:aws:lambda:us-east-1:269266452438:function:CreateSlot"
            Next: "SearchSubscriptions"

I have tried using both function names createSubscription and CreateSubscription, but nothing helps. I checked issues previously raised, but doesn't help much

I am tried using versions 2.1.2 and 2.1.1, but doesn't work. Any help would be appreciated