Thanks for contacting us here on the forums! Viewing on the Chromecast is only able to be done by casting the stream from a mobile device, such as your tablet, which is why you are having issues using your Windows 10 computer to achieve the same result. Here is an article that gives all of the frequently asked questions about using the Chromecast with your Slingbox:
Hope this helps!! If you have any further questions, please feel free to contact us back!
Sling Media Technical Support