Please try fully exiting the channel (press the "home" button on your remote) and then going back in, which will refresh the content. You can also visit Home/Settings/System/System Update/Check now—this will update the system to the latest version of the Acorn TV app.
Users with original/classic Roku players: as of May 30th 2015, Roku has discontinued software and channel updates to Classic Roku players, made before May 2011 (models N1000, N1050, N1100, N1101, 2000X, 2050X, 2100X). These models will no longer update with new content.