How to restore a btrfs-snapshot which is on an other drive?

Hi! If I try to restore a snapshot of my datadir that is on a other USB drive, it doesn’t work. I tryed it like it was described in the documentation of NCP:
sudo btrfs subvolume snapshot /media/Stick8/snap/hourly_2018-12-11_031701/ /media/SSD/ncdata

Create a snapshot of ‘/media/Stick8/snap/hourly_2018-12-11_031701/’ in ‘/media/SSD/ncdata’
ERROR: cannot snapshot ‘/media/Stick8/snap/hourly_2018-12-11_031701/’: Invalid cross-device link

And if I just move the snapshot to the location the datadir should be, it’s an internal server error. So the directory is there, the Data is there but it’s not working.