This restore option only becomes available once a restore has been selected that is valid for the currently deployed restore appliance. This involves a number of checks that must be valid. These values can be mostly observed in the GUI on the restore Backup History.
Validate the backup file you are using by checking two data points. The GUI will show you the restore files including their FQDN or IP. The other thing to validate is the backup location will generate a folder with the following format in the naming.
<NSX Version including build number><IP stack in use (IPv4,IPv6 or Dual)><Old appliance ID><FQDN or IP>
eg.
Folder Name - 4.2.2.1.0.24765087-Dual-fa961d42-XXXX-XXXX-XXXX-XXXXe8ddb89a-nsx-mngr-01.example
Environment - 4.2.2.1 version, dual stack, with FQDN publish set.
Folder Name - 4.2.2.1.0.24765087-IPv4-0cac1d42-XXXX-XXXX-XXXX-XXXX8c4be86e-192.168.120.1
Environment - 4.2.2.1 version, IPv4 only, no FQDN publish set.
Folder Name - 4.2.2.1.0.24765087-IPv4-a8021d42-XXXX-XXXX-XXXX-XXXX3846999a-nsx-mngr-01.example
Environment - 4.2.2.1 version, IPv4 only, FQDN publish set.
Then ensure the restore appliance matches each of the values required by doing the relevant actions of the below.
More details on backup and restore procedure can be found in the admin guide Backing Up and Restoring NSX Manager or Global Manager.