Mojang has introduced a mandatory EULA you must accept before your server will start for the first time
In order to accept the EULA you must log into the control panel using the details from the server information email.
Once logged into the control panel click on the left hand side Files, then config files, then you should see a EULA option
1. Accept the EULA by Clicking on "Minecraft EULA" and selecting enabled and clicking on save in your config files in your multicraft control panel.
2. You will then need to start your server again.