Hi:
Temporarily disconnect the hard drive and see if the PC automatically boots from the M.2 SSD.
There are some model notebooks where the SSD does not show up in the boot options menu, and if there is an operating system on the 2.5" drive, the PC will always want to boot from that drive first.
Notebooks that come with dual drive configurations from the factory have no operating system on the 2.5" drive.
So if the notebook boots up and works fine with just the NVMe drive installed, reconnect the 2.5" drive and format it and then the notebook should boot from the NVMe drive and you can use the blank 2.5" drive for storage.