The ‘Store Credentials’ option was removed in 2017.1, I think. For the unattended robot, you have to provide the credential in Orchestrator, when you provision the robot and the attended robot will run under current user credential.
Btw, you have installed version 2018.1.3, not 2018.3.
The message at the bottom of the windows says the connection status of robot to Orchestrator. ‘Disconnected’ means that you do not have the connection set. You need to open Settings to configure the connection, but for that you need administrative rights.
Check the software requirements for 2018.1 version on Windows 2008 R2 you need also the update KB 963697 and the Desktop Experience feature.