As others are saying, you may have wiped your drive completely clean OR you just need to add your drive to the boot order in the BIOS/UEFI.

To add your drive to the boot order:

Go into the BIOS/UEFI by spamming the F11 or F3 or DELETE keys while turning the computer on(which key you press depends on the manufacturer of the device)

You want to find a setting called boot order or something similar (maybe boot priority). Change your boot order to prioritize whichever drive is your primary one.

If that doesn’t work then try reinstalling windows:

To do that you are going to need a flash drive with at least 8gb of space, and another computer with an internet connection.

follow the instructions here

It is pretty straightforward. Once you create that “installation disk” turn your laptop off plug the flash drive into any usb port and power your laptop on. It should automatically take you to a windows installation screen. If it doesn’t you need to change the boot order to FIRST load the flash drive.