Shader Graph error when installing


I’m using Unity 2019.1 for sure. When i try to install Shader Graph or Light weight RP with Package Manager I got this errors:
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What should I do ?

Try creating a new project with LWRP selected. For an existing project, use package manager to import Lightweight RP, then go to Project Settings → Graphics and select the RP asset to either LWRP high, medium or low. THEN import Shader Graph.