Dear Bernat, I have the very same problem. I downloaded the editor and everything works except for the "text" block. Is there something I can do in order to make even this block work in the offline version? This block is unfortunately vital for the lessons I have to start in a few days.
Thanks in advance
Stefano
PS: https://file.io/5eXNzc is the project that works fine online but doesn't work offline.