Yes, everything loaded for me today on the Screambox website. It was an issue on my end preventing me from seeing the available titles. Thanks for verifying that it was working for you.
May need to contact Screambox at their Support page https://support.screambox.com/hc/en-us in order to find out the status of their Roku channel/app. They may simply have to update it for the newer 11.5 OS. (many channels/apps had to migrate from deprecated/old coding in order to continue working on the Roku OS.)
Looks like they previously supported most Roku devices using OS 6.2 and up so I would tend to think their channel/app became outdated and was either removed by themselves or Roku because no longer compatible with 11.5. https://support.screambox.com/hc/en-us/articles/4407604099995-Roku-Device-Compatibility-with-Screamb...
Until resolved, you can certainly continue to cast it from their website to your Roku device, or alternatively, play it on a laptop and attach HDMI cable directly to your TV (bypass Roku). Both these methods will at least allow you to use your subscription until you hear back from Screambox and watch on your TV.
Feel free to post an update if you learn anything.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941