If you cannot re-enable your server in the panel, this is generally due to an outstanding balance on your latest invoice. If you do not pay your invoice, after the second invoice reminder, your server will automatically be set to suspended. This means that you cannot access your server, as it will be offline. This can only be resolved by logging into the billing panel and paying any outstanding invoices. After doing this, your server will be automatically reactivated and available to access within a few minutes.