Problems with UnityPackage Mobile.Notifications

Hello guys! I have a custom unitypackage, with some tools, one of such tools it's a manager that uses the package mobile.notifications.

I've imported this custompackage on an empty project for testing and i'm getting lots of errors with the notification packages, that is not finding the the types or namespaces.

Any hints on this would be really appreciated. i'm kind of lost with this... dont know why, even when ive declared the dependency and imported also the notification package it isnt working.