Checkout object unknown in shopify Graphql app's playground

[Lallawmzuala]

I'm trying to query the Checkout object of a customer and when checkout is completed, It would mean the order is placed and would display some UI accordingly. I've been using 2020-07 version of the Shopify Graphql app to query the details and was working fine at the beginning(probably around 07-2020) .But when I tried to run the same query again today from the Graphql app's playground, it's telling me that the Checkout is an unknown type. I switched to Storefront api but permission was denied. The query that I used is given below(I pass the checkout Id accordingly)

query($id: ID!){
  node(id: $id) {
    ... on Checkout {
      id
      email
      appliedGiftCards {
        amountUsedV2 {
          amount
          currencyCode
        }
        balanceV2 {
          amount
          currencyCode
        }
        id
      }
      requiresShipping
      completedAt
      createdAt
      currencyCode
      lineItems(first: 10) {
        edges {
          node {
            id
            quantity
            title
            variant {
              id
              priceV2 {
                amount
                currencyCode
              }
              title
              image {
                altText
                originalSrc
                id
              }
              compareAtPriceV2 {
                amount
                currencyCode
              }
              weight
              weightUnit
              availableForSale
              sku
              requiresShipping
            }
          }
        }
      }
      note
      webUrl
      updatedAt
      totalTaxV2 {
        amount
        currencyCode
      }
      totalPriceV2 {
        amount
        currencyCode
      }
      taxesIncluded
      taxExempt
      subtotalPriceV2 {
        amount
        currencyCode
      }
      orderStatusUrl
      order{
        fulfillmentStatus
        shippingAddress{
          formatted
          formattedArea
          name
          longitude
          latitude
          firstName
          lastName
        }
        lineItems(first: 200) {
          edges {
            node {
              title
              quantity
              variant {
                image {
                  originalSrc
                }
                priceV2 {
                  amount
                }
                compareAtPriceV2 {
                  amount
                }
              }
            }
          }
        }
        financialStatus
        phone
        originalTotalPrice{
          amount
        }
        currentTotalPrice{
          amount
        }

        currentSubtotalPrice {
          amount
        }
        subtotalPriceV2 {
          amount
        }
        totalShippingPriceV2 {
          amount
        }
        orderNumber
        
      }
    }
  }
}