How to fix window that has dropped down

[OM2]

We had new windows fitted just a year ago.
One window has somehow dropped down.
I can't see anywhere on the window where I can adjust a screw to move up or down.
(I can't get hold of the installation company.)

I need advice how I can fix - there must be a way of adjusting.
What further information do I need to give to help answer?
What other parts should I photo?

See below for picture.

Thanks.

 

[flameport]

Window hinges do not generally have adjustments, and even if the did, that size of gap is far to large for any adjuster.

Open the window (keeping hold of it) and look at the hinges - likely that one has broken, or has become detached from the frame.

 

[Gazman16]

Looks like it hasnt been "Toe & heeled" correctly http://www.glassandlock.co.uk/how-to-toe-and-heel-a-door-or-window/

You will need to take out the side beads and the top bead, lift the sash and force some packers between the glass and sash at the top on the handle side.
Put in enough packers for all the corner welds to line up, Then refit the beads.
5 min job for a pro. Getting the beads out is the trickiest bit.