Z-Suite won't load .3mf files on mac



I used to use netfabb azure website to fix my stl's, but that seems to have finally gone forever (YAY). So after exhausting all other options, I realised Z-Suite says it supports 3mf files but upon opening them in Z-suite I get the following error. This has basically prevented me from 3D printing at all - any help would be much appreciated. 

I’m on MacOS Sierra, Z-Suite v1.70