What macOS installer are you booting? You need to be booting from a macOS 10.13+ installer when you have an NVMe SSD installed internally. Even if you are using Command + R or even Command + Option + R to access Internet Recovery Mode, some Macs will still only boot to the online installer for the OS which originally shipped with the Mac, which for a 2014 laptop is macOS 10.10 which has no understanding of NVMe SSDs.
So if you cannot boot to the online Big Sur installer, then you will need to create a bootable macOS 11.x Big Sur installer using the instructions in this Apple article:
Create a bootable installer for macOS - Apple Support
Even if you are booting into a macOS 10.13+ installer you may need to erase the whole physical SSD. Within Disk Utility you may need to click "View" and select "Show All Devices" before the physical drives appears on the left pane of Disk Utility. Erase the whole physical SSD as GUID partition and APFS (top option).
If none of this helps, then try an SMC Reset and a PRAM Reset (hold the PRAM Reset for at least three chimes). Try to perform the SMC Reset first, then when you power on the laptop perform the PRAM Reset so they are done back to back without the system even attempting to boot beyond that point. Years ago I had an early MBAir with an OWC installed and this was the only way to get it to work the first time since performing the resets separately did not do anything (OWC support told me this, it was the only time I ever found it necessary).
Edit: I just want to confirm that macOS 11.x Big Sur was actually installed on this laptop previously (at least one time as opposed to only having it cloned).
