It's up and running !
Following your reply, I opened the Ruby console (this was new for me :-). At the end of the generation process, the code displayed was : FFmpeg = false.
Indeed I had to authorize access to FFmpeg, couldn't do it on the apple preference system, security window and I didn't want to start writing codes, no experience at all.
There are a lot of stuff on YT about installing FFmpeg on Mac.
I had a go, I downloaded the FFmeg EXE prog. Then I directed Animator to it and using the red FFmpeg button... and finally got the window authorizing the access !
I ran the video generation again and Ruby showed FFmpeg = True !
I still have to press the "interrupt " button at the end to save the video file but all ok.
It's strange that using SU "gestionnaire Extension" all looks fine with your files, which are both signed ?
Did I miss anything in the installation process ? Thank you Fredo