Learners are invisible, when I try to assign them a learning item

Summary

Learners are invisible, when I try to assign them a learning item

Content

Hi,

I have create a learning item and I want to assign this item to a group of learners, but when i try to select them with any type of search, I can't find them. Only learners from HR Department with HR role are visible.

How can I solve this issue?

Many Thanks

Federica