Hi pheonix7610,
subscription users are not allowed to install test versions, but only stable versions. Since 3.08 with new Metal and Toon shaders is not yet stable, if you want to try the new features, you need to export your scene from Live View in .ocs or .orbx format, and install Standalone Subscription version 3.08 test 6 from the following link:
viewtopic.php?f=33&t=64362As soon as 3.08 SDK will be stable, a new version of subscription plugins will be published.
ciao beppe