nu1301 error in china and encoding problem

[Imitater967]

error NU1301: δ�ܴ�Զ��Դ��https://api.nuget.org/v3-flatcontainer/msbuildforunity/index.json�������йء�MSBuildForUnity������Ϣ��

it shows this error, and i can't visit it mannually.
also encoding problem