Your example doesn't work.

In the left and right joins, Father 3 is displayed.

With the isnull(....), there is no child record in the son table to apply the isnull too, therefore,...

dbo is the database owner.

Change the database owner using sp_changedbowner.

Managed to fix this myself, if anyone else has the same problem here's the problem with my code.

In order for the server permissions to work using certificates, you need to...

Thank you for the reply bitbucket.

This does indeed hide the error message when the file is viewed in Excel, but the values in the cells are still stored as text....