Development store "Checkout System disabled: Merchant's trial period expired"

Hi All,

In my development store, when I click on “Checkout”,
I get this error: Checkout System disabled: Merchant’s trial period expired.
I am unable to test my checkout.

How to solve it?
I read somewhere here that if it happens then I need to contact you to fix it

My store link: https://anans-test.myshopify.com/

Thanks,
Ahmed