Server admin tool lost in configuration panel


Using ‘configuration’ in the left side of GRAFANA screen I cannot see ‘server admin’ any more.
I think this occured after having created an admin01 (which has Admin role) then deleted the original admin user by mistake.
I tried to use “allow_org_create = true” or recreate the admin name : same issue.
Could you help me on this subject (grafana 5.4.3) ?