Yes, Get Map Data is available in the trial version, which is the Advanced version of CityEngine. You will also need an ArcGIS Online account. With the free public account, there is access to the basemaps and the OpenStreetMap data. However, to access the elevation data, an organizational account for ArcGIS Online is required. Trial access for this can also be obtained if elevation data is desired.
Please make sure the your user login name is correct. The login from CityEngine is case sensitive, whereas on https://www.arcgis.com/home/signin.html it isn't. You can see your exact user name on ArcGIS online under My Profile.