Activation codes for Steinberg products are unique, one-time use strings tied to a specific MySteinberg account . Publicly shared codes will not work because they have already been registered.
If purchasing Cubase is not currently an option, there are many excellent, legal, and completely free Digital Audio Workstations (DAWs) that you can use to make professional-quality music. These are legitimate programs, not cracks, so there is no risk to your computer or your legal standing.