Hi Dante,
For the cross application relationship do the users who aren't seeing the value have permissions to see that field in the child app? What you might want to do is make sure you have a role in the child app that is able to see the records on that table and then in the cross application section of the app permissions for the child app make sure to add the parent app in with the role that is able to see the values on that table and if this field relies on any other tables or fields within that app to make sure it also has permissions to those. It sounds like most likely it isn't seeing the values in the child table due to the parent app not having permissions set up for it. I hope this info is helpful.
