In pak 64 there are no trams and if they do, horse-drawn trams and segments of tram that are not complete. What has happened ????
I might state the obvious here, but did you electrify the tram depot? If not, then you might see this behaviour. If it's not electrified, you might as well read the beginner's guide or the reference guide. As far as I remember this is mentioned there.
If you did electrify it, then something else is wrong. You might be simply too early (timeline on, some early year), or your pak 64 is broken. A redownload would be a solution then.
But anyway, there are trams in pak 64.
Oh yeah. There are trams in pak64 :P. I'm terribly sorry for the interruption :-[.