Automation of subscription order

[mabidlax]

I am developing custom subscription app, created selling plan groups, selling plans, associated products to the plan and generated sample order.
the issue arises in automating the order process as the next billing date arrives there is no new order for the subscription.
some information regarding the app:

1. app is created through shopify cli using PHP template.
2. API version is 2023-07
3. enabled shopify payments test mode
4. as in the shopify docs its mentioned that if selling plan product is purchased through checkout shopify itself generates a contract and shares it through webhook so I skipped the contract creation step which is mentioned in shopify docs. doc link
   

I am confused with the contracts, can someone please give me a brief understanding of it, like should we create contract through GraphQL even when shopify is created one, and if selling plan gets updated should the previous contract also deserve an update or only the active one.

have one more question, if I should generate the contract my self then what is the purpose of shopify generated contract and then what is the need of using shopify subscription API

[Brian_S]

You are required to create billing attempt for subscriptions. There's no automated billing. 

Check out the Shopify documentation on subscriptions, specifically the image that indicates the core responsibilities of the app in the lifecycle of a subscription:

https://shopify.dev/docs/apps/selling-strategies/subscriptions/modeling#lifecycle-of-a-subscription-...