Weblogic: Deployment State New Issue

When I tried to deploy an demo app to my newly set up Weblogic, I encountered a weird situation where the deployment state is New/Prepare, not Active as expected.
After first, I thought there were something wrong with the app itself. Then I thought there was something wrong with the deployment method: I tried auto deploy, web console.
However, it turned out that the managed server (TestServer) that I tried to deploy the app on was NOT RUNNING!
To check out, go Environment (under Domain Structure) > Servers (on the right side)

Solution: You can turn it on from command line/scripts or from the web GUI console

From the web GUI console, Environment (under Domain Structure) > Servers (on the right side) >

Control (next to Configuration tab) > Check the one you would like to start > Start

Now I can get my app deployment state back to Active again!