How can I fix a radiator upstairs that won't heat up?

I've checked for trapped air but none. The thermostat valave is new and on full -all other radiators are working

Normal ch system from gas boiler

derek, October 2008

I also have 1 cold radiator.
I did that I turned off 5 "working fine" rads, but still nothing, not even the slightest bit of heat. Mine is a rad in the attic but the rad in the attic bathroom works fine. i have bleed the rad. Could i have a blockage maybe? as there is no heat even in the pipes that feed the rad!.

Steve Tew, October 2008

Turn off rads that work might force through
make sure lock shield valve is open on the other side of rad

a, October 2008