I Merged this thread from the Q&A
Is it the “Student” [free] or the “Student/Teacher” [price vary] version?
The free version has no option for plug-ins.
For the serial code, please contact MAXON directly. Perhaps follow the link above, your country, and fill in the problem perhaps in the “Please explain the role…” field.
Please note that I’m not familiar nor connected to this part of the distribution and I might be wrong.
I hope things will work out fine for you. (I have as well answered your PM.)
All the best