The version 2017.1.0f1 posted on July 11th shows “Error loading Mono” when opening project. Same project works fine with 5.6.2xf1. The log just shows that mono was unable to load /opt/Unity/Editor/Data/Mono/MonoEmbedRuntime/libmono.so. The file exists, has permissions and its i386:x86_64 compatible.
The point is that Unity 2017 changes the folder where the mono lib is to this one:
“/Applications/Unity/Unity.app/Contents/Frameworks/Mono/MonoEmbedRuntime/osx”
But it seems that there is an internal bug in Unity when it tries to load native libraries for MacOS and it is trying to find the library in the old library folder:
“/Applications/Unity/Unity.app/Contents/Frameworks/MonoEmbedRuntime/osx”
Without the previous “Mono” folder.
The only way to have this working is to copy the MonoEmbedRuntime folder to a previous directory.
Please check this for future patch or release builds of Unity.