Why does is iphone 5S not restoring backup from iphone 4?

Trying to restore backup in cloud from iphone 4 to 5S but it keeps stopping and nothing is coming down - all songs say "download error" or "processing". Been like that for 3 days, tried switching on and off several times but to no avail. Apps came down fine but that's it. Am using fibre broadband so don't think it's a connectivity issue. Help!!