Hank here from Shopify.
When did you first notice this, was it just when you entered your payment information or did you receive any error messages in your admin prior to the store going offline?
Since then, have you received an email from the accounts team at Shopify? If you had, my advice would be to respond directly to this email with any questions you may have, as they are best equipped to deal with any account queries. Note that sometimes emails will get sent to your junk/spam folder.
However, if you have not received an email, let me know, and I can look into this further for you.