After choosing to switch to the New User Interface, access to the application is denied.
If a proxy server is activated, it may block the access to the new interface of the Rainbow Application.
How to fix:
Check the proxy server configuration and allow the access to the url of the new User Interface.
Old user interface url format is as follows: https://web.openrainbow.com/app/1.76.2/index.html
New user interface url format is as follows: https://web.openrainbow.com/rb/2.76.4/index.html