Mes données ne s'affichent plus après mise à jour

Jerome speaks French, so he may answer better.
But for now: try "clear all filters"; it is a button now, with 3 little bubble icons in a diagonal line. You may be hiding the tasks.

If that does not work, maybe remove (or rename for now) your .ini file, see:
https://answers.launchpad.net/taskcoach/+faq/1061

Also: we mostly do support here:
https://sourceforge.net/p/taskcoach/support-requests/

Thanks for your answer
This did not solved my problem.
I had already read and tried the other soluce (deleting.ini file). To no avail.
Here is what I did that worked :
I began a new session with the newly downloaded version.
The page what completely empty of any data, though my .tsk file was present and I could open it and check it was the right one with notepad++. My old file was called katryne.tsk.
With the new version, I started a fake new task, then saved my datas under the name katbis.tsk.
Then in the explorer I deleted katbis.tsk and renamed katryne.tsk to katbis.tsk.
And now everything is in order, I recovered my list of task just as it was yesterday.
It's not very easy, maybe because it's a portable version. I would appreciate a more practical system of updating.
My sincere thanks to the coders and to all the members of the support team.

Ok, sorry, I think I made this more complicated than it should be.

Probably, you just didn't open your old file. You could have just used the Open menu command to choose your old file, because it didn't load automatically.

Cordialement,
Aaron