My Newline panel is showing “Authorisation error” when I open Newline Cast.

The error shows the application cannot communicate with our server to perform activation. This could be a firewall issue with your network. Can you check the following requirements with your IT department?

https://support.displaynote.com/hc/en-us/articles/360017853178-Firewalls-and-proxies-

Alternatively, you can connect your Newline screen to a mobile hotspot (from your phone) and try to activate it once more. Here are guides to activate a mobile hotspot:

Iphone/iPad: https://support.apple.com/en-gb/HT204023

Android: https://www.androidauthority.com/mobile-hotspot-setup-631280/

This turns your phone into a separate Wi-Fi option from your network. From here, you can connect your Newline display to the hotspot the same way you would connect any device to a Wi-Fi network. Then you can activate the Key/proceed with activation.