Calor gas heaters

I hope someone can help! I have a calor gas heater and it's just run out of gas. I've put a new bottle on, fitted the valve back (which isn't very old) and it won't light! The bottle has been stored outside and may have got wet although there was a plastic protective cap on it. Does anyone have any idea why this has happened and what I can do? I'm getting cold

Once butane gets down to about 5ºC or lower it wont turn from a liquid to a gas easily.
Try warming the bottle up with an electric fan heater or something till it gets going

Thanks for the reply but it isn't that cold here. I have checked everything I possibly can and as I said, it was working with the old gas bottle before I changed it. If anyone can think of anythin else that it might be, please let me know, I'm getting desperate