Hi and welcome to the forum,
The Grace Period has never worked automatically for the LE and AI editions, as far as I know.
The first step is to have the license registered in your MySteinberg account. If this is not the case, do so as mentioned above.
Once you have it registered, ask for the free update to the latest Cubase LE 13 (and most important to the new Steinberg Licensing System) in this thread.
By aware, Cubase 13 is 64-bit only (not as Cubase 5, which was both 64- and 32-bit). So I hope, you have 64-bit system.