Unauthorized error on fresh installation #1611

I've setup a brand new virtual machine scale set (vmss) running Cent OS on Azure. The scale set has 3 instances and I ran the installation script on all 3 of them. The vmss is running behind a load balancer.

I've used the createSiteAdmin CLI command to create credentials, but when using them to login I'm getting an "Unauthorized" error. Looking in the browser dev tools I see all the calls on /api get 401 Unauthorized errors.

Anyone any idea on how to resolve this issue?