Cannot boot into lvm encyprypted root partition

I cannot boot into lvm encyprypted root partition:

            mount: mounting "/dev/mapper/vg-root on /root failed: No such file or directory␍␊

            Failed to mount "/dev/mapper/vg-root as root file system.␍␊

The flollowing step i made  (short version)

- create the lvm partition

- mount lvm partition and and copy file system auf lvm partition, bind /dev, sys, proc

- chroot in the lvm root partition (vg-root)

- change /etc/fstab :  insert

               /dev/mapper/vg-root / ext4 errors=remount-ro 0 1

                UUID=<UUID-Partiion> /mnt/mnt ext4 defaults,noatime,nodiratime,commit=600,errors=remount-ro 0 2

               #UUID=<UUID-Partiion> / ext4 defaults,noatime,nodiratime,commit=600,errors=remount-ro 0 1

- create the initramfs:

               update-initramfs -u -k $(uname -r)

- change armbian.txt:

             rootdev="/dev/mapper/vg-root cryptdevice=/dev/mmcblk0p2:lvm"

During boot, the device ask the PW:

             Begin: Mounting root file system ... Begin: Running /scripts/local-top ... Please unlock disk lvm: ␍␊

After inserting the password, lvm seems alright ("cryptsetup: lvm: set up successfully␍␊done.␍␊")

But the boot file system is not fount

               Begin: Running /scripts/local-premount ... Scanning for Btrfs filesystems␍␊

              done.␍␊

               Begin: Will now check root file system ... fsck from util-linux 2.33.1␍␊

               Checking all file systems.␍␊

               done.␍␊

              mount: mounting "/dev/mapper/vg-root on /root failed: No such file or directory␍␊

              Failed to mount "/dev/mapper/vg-root as root file system.␍␊

i am very grateful for any comments and tips.
I have already done such LVM boot encryption 2 years ago on Pine 64 and Pine LTS.
BUT NOW I HAVE NO IDEA HOW TO LOOK FURTHER.