Trying to change my wallpaper from the android Settings app, I tap 'From Gallery' on the film strip at the bottom which launches Google Photos. From there I select the photo I want, and it returns to the settings app with the message "Unable to load photo."
If I switch the default photo app to Gallery and use it to select an image stored on my phone, it works, but that doesn't allow me to access photos from my Google account.
If I launch Photos itself I can set an image as the wallpaper, but that doesn't let me change the lock screen unlike going through Settings.
It all worked fine yesterday and I'm not sure what's changed. Restarting the phone hasn't helped, and neither has uninstalling and reinstalling Photos or clearing its cache.