Issue syncing Domain Users Group from onpremise to Azure Active Directory

Hello,

we need to assign a group license Office 365 A1 to all users of our organization. So, we want to create an automatic assign the license to group Domain Users (in spanish Usuarios del Dominio).

This group is in OU Users that is synced, and others groups in the same OU exists in Azure Active Directoru Groups Directory. But Domain Users does not appear.

Is there any restriction to sync system groups? Or any limit of group members? Is there any other way to assign a license to all users?

Regards.