Mathcad 15 student product code invalid

We had ordered a bunch of product codes (student license) and experience the problem that they are not accepted when we try to install Mathad 15.

The product codes all start with MP010111EA.... an because of the MP I suppose they are intended for MC Prime. We are not (yet) interested in Mathcad Prime and don't want to have to install Prime first simply to get a valid license file which then works for MC 15 too. It is also not reasonable to have every student to call technical support, give them his product code and MAC-Adress to get a valid license file.

I thought that Mathcad 15 and Mathcad Prime share license file AND product code but it seems that this is not true at least for the product code.

Are we doing something wrong or is there a simple solution available?

Thanks an sincerely

WE