Hi everyone,
I have opened the file in question in my windows Rhino and the ‘top’ viewport appeared floating on top. I resized all 4 ports and saved the file. I reopened in Rhino 5.2 for Mac and it opened with all viewports showing and the Layout panel floating on top also depicting the ‘Top’ view. It must be file specific because other files I opened displayed normally.
Anyway, all is good.
Thanks Rob K