You could try a Planner Rebuild as explained here: https://www.sky.com/help/home/sky-tv/sky-tv-plus/sky-plus-watching-sky-tv/sky-plus-recordings/articl...
If that doesn't help, a full System Reset, as in the same help guide would be the next step.
If neither help, you'll need a new Sky box - that means a Sky Q box or a Sky Puck, as you can no longer use a replacement Sky+ box. Best speak to Sky about your options.
