creating a partition makes the server unbootable

Question

I have a server that comes with a softRaid of 2x450gb nvme disks. Since all my data is backupped, I don't need the raid and I want to use the full space instead.

From the hosting (OVH) control panel I selected to format only one disk, and what I got was:

~# fdisk -l
Disk /dev/nvme0n1: 419.2 GiB, 450098159616 bytes, 879097968 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 2791B286-8A53-4943-A74D-A3E86200E692

Device             Start       End   Sectors   Size Type
/dev/nvme0n1p1      2048   1048575   1046528   511M EFI System
/dev/nvme0n1p2   1048576   2095103   1046528   511M Linux filesystem
/dev/nvme0n1p3   2095104 878039039 875943936 417.7G Linux filesystem
/dev/nvme0n1p4 878039040 879085567   1046528   511M Linux swap


Disk /dev/nvme1n1: 419.2 GiB, 450098159616 bytes, 879097968 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 2ADB5903-8173-44BA-907C-945EFA2DD7ED

Device         Start     End Sectors  Size Type
/dev/nvme1n1p1  2048 1048575 1046528  511M EFI System

so I created a partition on nvme1 and formatted it:

root@web08:~# fdisk /dev/nvme1n1

Welcome to fdisk (util-linux 2.31.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): F
Unpartitioned space /dev/nvme1n1: 418.7 GiB, 449561271808 bytes, 878049359 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

  Start       End   Sectors   Size
1048576 879097934 878049359 418.7G

Command (m for help): n
Partition number (2-128, default 2):
First sector (1048576-879097934, default 1048576):
Last sector, +sectors or +size{K,M,G,T,P} (1048576-879097934, default 879097934):

Created a new partition 2 of type 'Linux filesystem' and of size 418.7 GiB.

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

root@web08:~# mkfs -t ext4 /dev/nvme1n1p2
mke2fs 1.44.1 (24-Mar-2018)
Discarding device blocks: done
Creating filesystem with 109756169 4k blocks and 27443200 inodes
Filesystem UUID: 57d73a12-ad8b-4bf3-8daf-ca0081b0b17e
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
        102400000

Allocating group tables: done
Writing inode tables: done
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information: done

Now, if I reboot the server it doesn't boot anymore, without even putting the new partition in fstab (if I put it in fstab and I launch mount -av it mounts the partition without any problem)

What can it be?