iTunes does not show 2020 backup for iPad 1st Gen

Impossible to restore old iPad 1st Gen backup:

The Backup folder was created by iTunes during 2020 and is present in its original location.

The iPad 1 is from 2011 and has the latest supported iOS version 5.x.

Process:

1. iPad 1 connected by USB to a Windows 10 64b machine.
2. Latest iTunes (for Windows) launched and connected to the iPad
3. In iTunes: Edit-Preferences-Devices - the iPad 1 old backup is not visible.

Other backups (from 2017 and 2018) of old iOS devices do appear in the list.

-Impossible to restore the old backup to its original iPad device.