You might need to use the latest version of the 3DObject addon also, can you try that?
I have the 3DObject addon 2.34.1
exemples that doesnt work for me
3DObjectNodeDisable.c3p
PrefabDemo-02.c3p
this is the message I got
"Failed to open project. Check it is a valid Construct 3 single-file (.c3p) project."
Ah, these projects are saved in later beta versions, I use: https://editor.construct.net/r323/
