I Inform this forum that I found the cause of my problem …
For creating the video, the background process requires setting a variable written in the settings.ini file:
; Base URI to use for loopback requests (background processing, video creation, etc).
; This is mostly used when the pages are behind authentication and need another path
; for processing background tasks.
[color=#FF0000];[/color] local_server=http://X.X.X.X
In my case I did not notice that the line was commented ([color=#FF0000];[/color]) and there is no warning on the lack when you make the video request