If your account is locked, then that means your account has been flagged due to unpaid invoices. If you rather see “user blocked”, then check this article. 

Your unpaid invoices need to be paid fully before Servebolt can reopen your Control Panel access. Unpaid invoices may also lead to closure of your website. 

To regain access to your account then you would have to click the blue button below where it says “Add a credit card” and add a valid credit card. When that is done and your invoices have been paid, let Servebolt Support know and they’ll reopen your account.