If other attributes are loading successfully but a few specific ones are failing this could be because the mapping to the connector itself is misconfigured.
1) Log into Identity Portal Admin UI
2) Click Setup-> Managed Object Attributes
3) Find the attributes that are failing. You need to verify the attributes match the attributes from the connector.
4) You should notice a difference, make the modification and retest. You should notice the N/A now populates the correct values.