Hello,
Page where you can see the issue (you have to be login)
https://www.zorntt.fr/cal-prochains-evenements/cal-anniv-des-membres
In this case you will see picture 1
Now in admin -> Jevents config -> Tab "Event edit" you simply move the toggle "Accept multi-categories events" from NO to YES, see picture 2
And now on the page you will see picture 3 where all events of all my catégories are displayed in the right date range instead of the only one category selected in the range menu.
Many thanks for your help
Philippe