Hello,
Just to say that Rhino 6 can not open Rhino 4 files.
I need first to open the files in Rhino 5, save them under R5 3dm version, then open the latest in Rhino 6.
This is not a 6.18’s only issue, but is happening since very early WIP release of rhino 6.
Bellow some screen shots (in the order), or the messages displayed by Rhino6 when opening a rhino 4 file :
