Cryptsetup compains not a valid device

Hi,

We have a disk say /dev/sdx which is encrypted as whole disk (no partition)

Now after extending the disk and resizing the file system the cryptsetup comamnd compains that /dev/sdx is not a vaild LUKS device.

[xxxxxxxxxxxxxx]# cryptsetup luksOpen /dev/sdx sdxEncrypted
Device /dev/sdx is not a valid LUKS device.

Do I need to change anything with fdisk?

Quick Help is much appreciated.