Thanks for the notes here. Are other channels working correctly on your devices?
If so, this is likely an indication that their is an issue within the channel (app) that the channel provider will need to resolve. You'll want to contact PBS support directly to report this issue and request additional help. Each channel on the Roku platform is built and maintained by the channel developer themselves. They'll be able to best assist with any issues that you are encountering within their channel.
[Update] PBS Kids has just published an updated version of their channel to address the issue that was reported. Please visit Settings>System>system update>Check now to update to the latest version of the channel. This should clear up the issue you're seeing!