New heated windscreen. Only half working

I had a new heated screen fitted in the summer after a stone did a job on the old one.
Now the weather has began to turn cold and damp I have noticed that only the passenger side is working. On the old screen it all worked all the way accross.
What I need to know is whether this can be caused by a faulty connection?
If half the screen is working surely it means that the electical connection is working (is there just a single connector?).
Otherwise would this point to a faulty windscreen in which case I should call Autoglass and get them to fix it.
Are there any visible things I can check in the screen wireing before I make myself look foolish?

the windscreen has two heater elements, one for each half, fused and connected separately, you can see the plugs both sides below the screen if you open the bonnet, make sure the non-working half's plug is well connected/not corroded, eventually measure for voltage in it, fuses are F7 - LH element, F8 - RH element (engine bay fusebox)

No idea, but my screen only works on the driver's side! How much warranty do you get with replacement screens - mine was done a few months back? i.e. in summer

EDIT! THANKS sierraf I'll check them out as well.

12 months guarantee on new screens, the contacts corrode, take fuse out and clean up the connections then try,

Tnaks all. Contacts were starting to get a bit corroded. Some contact cleaner and gentle rubbing with a cloth has sorted out the probelm.
Many thanks. It'll be nice to be able to clear the screen without having to switch A\C on every now and again