Hi there,
I've been using archicad 14 (edu) for the last year, just upgraded to V16. I've carried over a project to the new program and all my materials properties have disappeared - all 3D objects now show only in a grey concrete-esque colour. I can't seem to create new objects in other colours either.
First check that the Renovation Filter of your 3D window is the same as your Plan view - it can override materials depending on their element's status.