Menu item not "clickable"

[jmls]

Hi all - have a strange issue with menus. In "horizontal" or "slim" mode, each menu option works just fine

ie click on "users" and I go to the user screen
however, in "static" or overlay mode the item becomes disabled

however, any "sub menu" on the toolbar works in both modes
any idea on what I'm doing wrong ? Using the "apollo" theme , the menus are defined in app.menu.component.ts
this.model = [
{
label: 'Home',
icon: 'pi pi-fw pi-home',
routerLink: ['/']
},
{
label: 'Users',
icon: 'pi pi-fw pi-users',
routerLink: ['/users']
},
{
label: 'Groups',
icon: 'pi pi-fw pi-users',
routerLink: ['/groups']
},