Answer:
Make sure that you have not inadvertently started the shortcut for the 2D version. 2D versions have a special license key. So if you have a "3D full version", please open the program by clicking the corresponding shortcut (see Image 02 on the left).
The 2D version is not available to students, as the 3D full version is always licensed. With this version, it is also possible to calculate planar models.