This has been resolved now.

WHMCS Staff are currently looking into our website issues.

We are working with WHMCS support to resolve an issue with our billing area this will all be live again in the morning, we do apologise. We were updating it and this broken it due to a underlying DB issue, on reverting to the DB backup that was made prior to this upgrade attempt it was broken still. We believe there is a underlying issue with our database and are awaiting support from the WHMCS team.

We're currently working on our client area/billing platform. We're working to get this back online as soon as possible.

Sorry for any inconvenience this may cause.