Most likely you are just missing the dm-thin-pool module in the dracut
initramfs image.

You can re-build it with the following command:

  # dracut -f /boot/initramfs-$(uname -r).img $(uname -r)

If the running kernel matches the initramfs you want to rebuild then
you can leave out the file and kernel version:

  # dracut -f

To build an initramfs with only the drivers that the running host
uses add the -H switch (the dm-thin-pool module must be loaded at
the time you run dracut for this to work):

  # dracut -fH

See the dracut man page for more details.