Yep, looks like there's an issue with the app. I haven't previously used it, so I don't know if it ever worked. I assume it did for you, based on your wording of the problem. Normally, best bet might be to contact Google or the app creator. As no creator is listed in the Channel Store, perhaps Tanner will jump in and offer some guidance. Or, perhaps other users have an idea?

I'm having the exact same issue and within the last 2 days. I also use photoview as a screensaver and I hope they fix it because I've enjoyed it thoroughly.

Mine started working again last night.

Thanks for letting us know what you're seeing. The channel referenced is developed by a third party, and is not published by Google. We've let them know about the issue, and they are working on an update to address it. 

Please continue to try checking for updates in Settings>System>System update>Check now, or try removing the channel, restarting your device, and adding the channel back once more. 

We're hoping this should be resolved soon and appreciate your patience in the meantime! 

Thanks,
Tanner