Thanks for your response, Andy!

However I don't think that this is a license-related issue because, as I've mentioned, other colleagues from my lab are able to perform Maxwell 3D simulations remotely. And (maybe I was not clear about that in the original post) I am using the same license as they are, which is a research license by the way - probably different from the student and demo versions you were referring to.

Fortunately, the Maxwell 2D simulations may just do the trick for the application that I am aiming for, but it would be really nice to have the 3D simulations ready to go if I needed. 
I will keep looking into that and any further help is appreciated.
If I find a solution in the meantime, I will make sure to post here!