Hello Alexander,
Yes i have one, on the side of my API, i said that he don't see the Key "File".
I have tested another method same axon process and same api server and it's work fine.
I think it's just the way that axon try to send the file that not align with my api and vice versa.
I want to try to send file with another api, i have to find one, to see if this is server side problem.
Thanks.