The Viki channel is not showing any episodes for the shows. You get the pop up message that says oops something went wrong. And clicking on others it shows no episodes listed.
The Viki channel occassionally has issues like this. Currently, looks like some "Popular" category content (on air) is playing, but not other on-demand.
You can go to Viki's Help page and on top right there is a "Submit a Request" link that will allow you to file a issue report. (https://support.viki.com/hc/en-us). One of the dropdowns will allow you to specify issues experienced on your Roku device.
The channel developer (Viki) is responsible for the channel maintenance so all fixes will come from them.
It does look like the content is playing correctly on their website though, so may have to try playing there and then cast to your Roku device or TV. Alternatively, stream from a laptop and connect directly via HDMI to your TV. (https://www.viki.com/)
Looks like the Viki issue has been resolved. Episodes seem to now be listed under their shows.