Not reading the disk

I purchased Recuva Pro as a hard drive failed on a laptop. I've replaced the drive in the laptop but wanted to try to recover the files from the failed one. I have an external StarTech sata to USB dock that the drive is in, which will normally read files or reformat drives. The drive reads "unallocated" in disk manager. You also cannot initialize it. When I open Recuva, it does not list the drive. The program is not seeing it. How do I go about trying to recover the files?

John B