Has the radiator just stopped working or have you just noticed? Is it only one rad or could it on a separate heating zone within the boiler...
Is it on the end of the pipe run?
Turning the others off is deffo the quickest way to check flow, balancing them is a case of narrowing the rad valves closest to the boiler and gradually having them more open the further down the pipe loop.
You could set all the other trvs to 1 and see if it gets hot, otherwise try diables suggestion of manipulating the trv mech with the cap off it, sometimes they're stuck but I think your installation is quite new.
Has the radiator just stopped working or have you just noticed? Is it only one rad or could it on a separate heating zone within the boiler...
Is it on the end of the pipe run?
Turning the others off is deffo the quickest way to check flow, balancing them is a case of narrowing the rad valves closest to the boiler and gradually having them more open the further down the pipe loop.