iphone 5 backup not uploading media files
I bought 50 gb online storage on my iphone 5(iOS 10.3.3) and made back up on it which is about 8 gb. I logged in my same icloud account in iphone 7(iOS 11.1.2) and updated the backup. For 2-3 days the media files were there but after 2 days they just disappeared. I reset and erased all setting and recovered data from 1st December 2017 backup. After the backup was complete it showed the media files of December 10th 2017. I did this continuously on iphone 7 and iphone 5, but nothing is worked. No matter how many times I recover my old data from 1st December 2017 it always gives me the 10th December 10th files, which I believe is impossible.
I request the management, please resolve this issue as my precious data of 2-3 years is stuck somewhere on an online server.
iPhone 5, iOS 10.3.3