Here are the notes from SAS TS when this same issue has happened to others:
If the column is on the input table but not in the metadata, the first thing to try is to import the new column into the existing metadata registration for the table. To do this, follow the steps below within SAS Management Console:
1. Under Environment Management, navigate to the table via the path:
Data Library Manager-> SAS Libraries->
2. In the right-hand pane you should see your table listed within the library listing. Right-click on the table and select "Properties".
3. Go to the "Columns" tab. Click on the "Import..." button at the lower right.
4. In the "Import Columns" window, you should be able to move the currently unregistered columns to the "Selected Columns" pane and OK out to save.
If this does not work for you, or the column is already shown in the metadata for the table within the "Columns" tab, you will need to unregister the table and import it back in. This could impact some references to this table, but that cannot be avoided. Therefore, if you can update the metadata by just importing the individual column, that is the recommended method to follow.