Finally I found a small software that makes the job excatly as I want !
http://linetracer.sourceforge.net/
If you need it, it's very easy to use !
Have a good end of year 2021 ...

Egor,
This is exactly whats happen to me.
But I use this fonction years and years without having mayor problems except some random instability...
If you have software improvement tell me !
All the best

Well, it failed completely for me, resulting a single line near the left edge of the image, and nothing more. There were definitely some changes made to the vectorization mechanism, with the best intents, which were quite a failure it seems.
I will try to bring some attention to it.
Thanks for the great usecase, this is going to help a lot.

Thanks again Lance !
You make the best...
It's the bad spirit of softwares :-)
But it's a real problem for my artistic project...
I hope Adobe will correct this strange bug that seems for me to be more a bad memory managment than a script error !
See you

Jean,

The best I can suggest is wait and see if one of the Adobe admins sees this posting. You can also try the community forums for suggestions, I know they keep an eye on those as well.

For what it's worth, I can successfully trace your latest sample gif, as long as it scaled up to ~2000mm or larger. Any smaller than that and it just produces a blank regardless of the settings I try.

It also seems to be working again for your original sample gif, as long as I scale it up to ~2500mm or larger.
The more I mess around with these gifs, the more I experience bugs. I seem to find that if it fails to trace, I have to scale up the image by another 1000mm to get it to trace again.

Thank you for the time you give me !
You are right...
The spacing between 2 lines was of 3 pixels as in the new file I attach.
What is strange is that it works ramdomly...
But now it works very rarely
It looks like a bug...
Do you know who alert for this kind of problem ?!
Thanks

Jean,

This image isn't working for me at all, even after re-starting illustrator. It still traces other images just fine.

Opening your gifs in photoshop I find that the lines are only 1px wide. In the original sample they're 3px from line to line, but in the second sample you provided the lines are 1px apart.

I wondered if perhaps that was too fine a pattern for the image trace to work with, so I re-sampled them to 300ppi and 600ppi in photoshop. I still don't get any results when tracing either one. Just a blank image.

I can't even get a result after re-starting illustrator, with either of the provided samples or my re-sampled versions.

There's definitely some sort of bug in the image trace code, it doesn't like these finely-spaced pixel art patterns at all.

Thanks lance !
But it doesn't work for me...
All my lines desappear... Even with your options...
Could you do the test for me to take my "Test_1040x800.ai" file
Place the file "Test_1040x800.gif"
Do the vectorisation with your options
And send me your result.
I'm sorry to disturb you like this...

Jean,

Playing around with this a little more and I find the same issue you have. Eventually it stops tracing at all and just shows me a blank space. I had to re-start illustrator to get it working again.

Jean,

Certainly. Attached is a screenshot of the settings as I last used them. They're very similar to the defaults for either line art or technical drawings though. I think the only thing I changed was the stroke px size, from 10px to 4px.

Thanks Lance for your answer
The trouble now is that I have no result at all.
When I do my vectorization no lines from my gif are vectorized.
They disappear...
Could you give the options you use to have your result and do you use my gif "sourcesfile.gif" as I gave it .
I'm not good in english and I'm not sure to understand all what you did...
Thanks

Something is definitely not working exactly the same as it used to. See my screenshot.

I took your original trace, and a copy of it w/ the strokes reduced to 0.75pt side by side
I then traced your gif myself with your settings. I seem to get 1/2 the amount of stroked lines as in your original trace.

I overlaid the original gif on both my trace and yours, to demonstrate that the 'new' trace seems to be a little more accurate, because even though it has fewer stroked lines, the amount of lines matches the gif itself.