Help, back window won't go back up!

[T4R]

Today when I was driving a warning light came on to say the back door was open. I stopped, wound the back window down, opened the door and closed it again. The light on the dash had gone out, but when I tried to wind the window up, nothing happened. There is a click when the button is pressed downwards, but nothing when pressed upwards. Rain is forecast later and I don't want to leave it unlocked. Any ideas on how I can get it closed again?

[T4R]

Update...

I just tried it again and out of desperation I put the key in and tried winding it up with the key and it worked!

So I then wound it down with the switch and it went down but not up again. With the key, it will not go down, but it will go back up again.

For now I've just left it up, but I will need to sort it at some point. Any ideas?

[Shadyadie]

Dirty contacts on switch

[shokenore]

Dirty contacts on switch

And the winner of the less is more is

[M8WHR]

It could be F*#ked.

[Sancho]

Could be the switch, could be the relay. Hidden behind the trim in the back left pillar.