We've had reports of a webserver error affecting new logins in the portal.
On further investigation this appears to be related to a code change completed on Thursday but only impacted customers that had credits on their accounts.
Due to a race condition, when this was trying to be rendered along with other portal data, it would timeout entirely exceeding the backend process time.
Our engineers have removed the rendering of the credit balance on the portal home screen for the moment and will continue to investigate this.
Update: This is now resolved and credit balanced are rendering as normal.