Add contacts does not work in MS Teams?

MS Teams has been installed on the server.

Some of my contacts are already imported in my user profile about 30pcs.
Now I want to continue adding contacts directly to "my" contact list via MS Teams.

I as a user select the following:

left screen "calls" => after that top tab "contacts"
click add contact
window "add to contacts" opens
enter a name or tel => message


"



no match found"
comes up =>
click on this window
after that a new
window
with 2 buttons
1x cancel or 1x add click on





button "add






"
new window with "add to contact" with a matrix opens to
fill in it applies
-









.









Full name *
-Company
-Title
-Telephone*


there



are also 2 buttons 1x Cancel or 1x Add
it is filled on my part all 4 positions
click on the button "Add

via a window the message
"Contact could not be added"
appears.

Who or what must be set up where so that new contacts can be added?

I do not have access to the administration level.
The specialist who has access also does not find this error, so my question to the forum, where this setting should be made, or is there a limit to the number of contacts. We are in the company about 60 people all manage your individual addresses/contacts.

Thanks for a possible answer and greetings
Mike