You can try bleeding a radiator when the heating is switched off the rectify the issue of airlocks – use a radiator key to open the valve and allow the trapped air to escape. Repeat the process with your downstairs radiators (which airlocks typically affect) until water leaks out from the bleed valve.
Alternatively, you can attempt to alleviate the air blockage in the pipes by switching off all the upstairs radiators that are in working order. You can do so by switching the thermostatic valve to zero and turning the lockshield valve clockwise all the way round using pliers. This will isolate your upstairs home radiators and can potentially tackle the airlock by forcing water to the downstairs radiators that aren’t working properly.
For a more detailed insight, explore our blog, Why are my downstairs radiators not working?