I'm Miles from the Social Care team at Shopify. Welcome to the Shopify Community!
When you've paused your store entirely, you're not able to access it in order to close it. To combat this, simply select a paid plan on the screen you see when you sign in. From there, you'll need to make a payment on the plan so you can access the store. Once you have access, you can go ahead and close the store. When the store is closed, you then need to reach out to the Shopify Support team who will be able to help you refund the payment you made to access your store again.
If you'd prefer to skip these steps, please let me know and I can email you to help you get started.
I'd love to understand why you're wanting to close your store. If you're struggling with something, or there's anything I can do to help out, please let me know.