Something doesn't seems to be right on those screenshots, you clearly have basically all your 15GB available but it still gives you the error, very weird.
I really can't think of a way to fix what it seems a Cloud/phone issue, but you can always try removing your Samsung Account from the phone (be aware that you will lose any Samsung Pay Cards info and data),then go to Settings-Apps and click the 3 dots at the top right and select Show System Adds, look for the Samsung account and Samsung push Services apps and on Storage clear the Cache and data, reboot and then add the Samsung Account again, see if that helps.
If not, only thing would be contacting Samsung Support. In the meantime and to be sure you have a good backup, just use the Smart Switch app on your Computer.
05-11-2017 12:54 PM