Most biographies have Jørn Utzon declining invitations to attend the opening and to later design the interiors in Australia (he did so remotely) after some major fallings out over cost with a new government after those that intially commissioned the work left.
eg: https://en.wikipedia.org/wiki/J%C3%B8rn_Utzon
https://www.abcalumni.au/utzon_finding_the_master_architect
It's difficult to imagine him turned away at the border if the record is accurate that he never attempted to return after leaving.