Why won't itunes recognize a perfect local backup file anymore?

Background: 1) had iphone disaster, it is now on life support; luckily have spare old iphone and needed to restore that phone from a local backup which is about 1TB in size. 2) While attempting to to restore old phone using local backup file, the desktop I was using had windows issues. 3) Copied the backup file to another computer but itunes won't recognize the most recent backup that I copied. Tried a different desktop, same issue. Tried a redundant file from an external hard disk and had same issue. I'm certain in previous versions of itunes, itunes would recognize a file copied into the appropriate directory. (My icloud account is 2 TB but it's impossible to get a full backup done because both ends are too slow for 1 TB of data; so, I do not have the benefit of a complete icloud redundancy for a complete restore. All my redundancies are local files.

TLDR: Had to recover a local iphone backup file which is about 1 TB in size from a failing desktop but cannot get itunes to recognize the file. The file is NOT corrupt. I copied file to the appropriate directory in windows that itunes usually places backup files. Why is itunes not recognizing the file???? Please get developers to fix this so users with a lot of data have local redundancy options. Are developers expecting a user to manually backup a 1TB worth of data on several different desktops for redunancy??? A process which takes usually about 7 hrs? inefficient and absurd. I just need itunes to recognize a perfect and recent backup file.