Google Calendar API - Service Account - Impersonate User - google-cloud-platform

Question

I have some difficulty to make work impersonate user with service account on Google Calendar API.
For give service account right on calendar, i created calendar with SA account for give it the full access rights.
I'm trying to add an event with any user of domain.
I'm setting to $client with impersonate user :
putenv("GOOGLE_APPLICATION_CREDENTIALS=JSON_CREDENTIAL_SA_FILE);
$client = new Google_Client();
$client->useApplicationDefaultCredentials();
$client->authorize();
$client->addScope([Google_Service_Calendar::CALENDAR]);
$client->setSubject(EMAIL USER TO IMPERSONATE);
But when i'm trying to add an events
$event = new \Google_Service_Calendar_Event($EventObj);
$event = $service->events->insert($AgendaID, $event);
GG Api return is "A service error occurred | reason:NotFound", it seems that user used can't found SA calendar ID.
Calendar ID ids not share with user used.
In Google Cloud Plateform, i created the service account and add delegation domain checkbox.
On IAM panel, email of service account is Owner. I gave to user used in my project role Service Account Token Creator or owner to try but same issue like describe here
On Google Admin, I gave to ID Service Account Scope needed in Security => API Command => https://www.googleapis.com/auth/calendar
I was thinking that when using setSubject, it's like using SA but like a user.
Insert work if i comment $client->setSubject(EMAIL USER TO IMPERSONATE);
I really don't understand why can't used any user of domain to write on SA Calendar.
Did i miss a configuration on google cloud plateform or google admin ?
Thanks for your help.