New SSD not showing

Your friend just needs to format it. All fresh disks come without being formatted so they don't appear right away. Can't really remember where was it on Windows, but he should check for disk management. The disk should be seen there.

There are also CMD commands but I should check them first.

Edit: Here are the CMD commands:

diskpart
list disk

That should show the disk. If that shows it, it also should be under disk management. He might have missed it.

list the specs of the old and new SSDs

Check if the disk is visible in the device (not disk) manager, try it with another PC

Make sure SATA Controller is set to AHCI in UEFI/BIOS

Is the computer booting from an SSD and the new drive is a mechanical hard drive? Maybe there is a setting in the BIOS that is preventing a mechanical drive from being used. I was searching online and someone said that disabling Intel Rapid Storage Technology fixed it for them, but I don't know if that is the issue here.

Try it
https://learn.microsoft.com/en-us/windows-server/storage/disk-management/initialize-new-disks