Links disapeared

I’ve got a zaclyx nextcloud account.
1/ I can’t connect my agendas with my colleagues , .
I did it once but after a while those persons were disconnected.
I try to did it again But now,it’s really enigmatic to understand how it works to connect with them The sharing logo opens a little window “partager avec des utilisateurs…”
and there is no place to choose how the person connected can access (read only, can edit…)
There is nothing to link to the contacts page.

The activity icon disapeared from the menu , as did the links to my colleagues on nextcloud last week after the maintenance day.

I am still under windows 7 on this computer , maybe is it the thing.
i am on firefox but i already tried under google , same problems.

you can imagine how problematic it is to work with.
thank you for your help

someone to answer my questions ?