Question on moving hard drives

I'm running Proxmox on a Lenovo ThinkCentre and I decided to swap the internal 256 GB 2,5" SSD for a 500 GB NVME.

I installed the new NVME alongside the old SSD, and formated it in ext4 with a single partition. I then proceeded to 'dd /dev/sda /dev/nvme0n1' and it went through without an error.

My impression was that it would clone all content from the old drive to the new, but it wouldn't boot the new drive. I then logged in and set a boot flag via fstab a, but that only helped me boot but the system gets stuck at "waiting for root file system".

Nothing is lost as the old drive still works fine when installed but how do I complete the swap correctly so I can go NVME-only?

Thank you!