In the Unity Editor menu, if you go to Edit > Project Settings > Services > Mediation or Services > Mediation > Configure to open the Mediation Adapter Configuration to attempt to install or uninstall an adapter, the UI might become unresponsive. This is potentially due to a corrupt file (which can occur when upgrading from 0.1 to 0.2).
To fix this, delete the file Assets/Editor/MediationAdapterDependencies.xml and then try to rebuild. After, go back to the Adapter Configuration screen and you can install or uninstall an adapter.
For more information, see the Unity Mediation documentation.