h'mmmm..
Well I just downloaded the latest tinycore-current.iso and booted to it.
I set the tce directory and loaded snap2usb extension
I selected the snap2usb icon which launched the script, a snapshot was saved to the attached USB drive
this is a snapshot of that snapshot

Since the extension performs as expected without dep's of it's own, this suggests that your system is missing a fundamental required component, agree?
I would start by comparing your loaded extensions with those of tinycore-current.iso