Acute 2R 2400 strobe not firing?

[letsbefriends]

I have a Acute 2R 2400 that I rented from school. One of the strobe heads does not fire ... but the modelling lights turn on. The other two heads work perfectly. Is there anything I can do about the one that doesn't fire? I am worried because I don't have the money to fix if it is broken. I didn't even start shooting yet.