I have elements which reference PI Tags in other elements to ensure that all elements reference the same PI Tag. When I create a view in SQL Commander all the values as needed are returned but when queried via a linked server only the values from PI Tags as data references are returned, those from attributes are NULL.
I would confirm your linked server is configured as per this KB first. Secondly, I am assuming the data coming back as NULL is tag data, is that correct? If so, I would check out the Network Manager Statistics on the Data Archive to see what user has authenticated to the Data Archive to retrieve this data and make sure it has permission to do so.