WooCommerce + Printful

Hello
Anybody knows why I get "JSON ERROR: Syntax error" on red stripe on printful site when I'm trying to connect my WooCommerce plugin to Printful?
I have Astra + Astra sites + Astra Template of store instaled and loaded and ofc WooCommerce and Prtintful.

Printful support does not help, sends me here...

https://drive.google.com/file/d/0Bz382j1jAeFLSlN4aHdnR3BBOVVFQ1cyZXplRDhjOS1tYlJN/view?usp=sharing

greetings