It usually means one of three things.
- You are booting into an older macOS 10.12 or earlier installer which is unable to communicate with a third party PCIe NVMe SSD that is installed internally.
- The internal SSD has failed.
- The install process on the internal SSD was aborted midway through phase one
Unfortunately you did not provide any details on the exact model of the computer or versions of macOS involved.....this is usually critical information that should be included whenever a person asks for help online.
If you are booted to a macOS 10.13+ installer, then launch Disk Utility. Within Disk Utility click "View" and select "Show All Devices". If you do not see the physical internal drive listed on the left pane, then the drive has failed. If you see "macOS Base System" as a volume on the internal SSD, then it means a previous installation was aborted. Erase the whole physical drive (Intel Macs only) followed by Quitting Disk Utility and selecting "Reinstall macOS".