The way I do it is the same as the method I posted about earlier in this thread. It works for me every time without fail.
Is iTunes on your computer updated to the latest version 12.5.3? iOS 10.1.1 is the latest version of iOS.
Yes, the iTunes in my computer is latest version 12.5.3.17, need update to ios 10.1.1 really ?
besides , i try to write the step again as below, pls let me know the step is correct or not. tks
1) Transfer purchase items
2) Sync
3) Perform the backup
4) Check the apps have reside in iTunes library or not.