am not sure what you mean by trying to add partition, or initialise, but would think this is something you should *NOT* be attempting.
Your priority here is to first recognise the disk and then copy the data off - nothing more!
If the disk is not that old, perhaps there is a problem with its enclosure. With the power off, disconnect and reconnect any plugs or sockets. This has cured many a fault.
Please advise back on progress.
Good Luck - Keep us posted.