AuthGroups init pb with shield:setup ?

hi,
(sorry for my poor english)
I use ci4.2.6 with shield.
getPermissions() give me null when I only map permission to groups in AuthGroups.php (it seems database isn't correctly populated with shield : setup).
But, getPermissions() is ok when I use addPermission() (database is correctly populated after addPermission() use).
Any idea ?
Thanks for advance.