My Worcester boiler won't start (with EA code), can you help?

My Worcester boiler is flashing EA code. I checked the condensing pipe is not frozen. The ~7cm diameter container is cleared of a lot of sands and water. But the boiler is still fashing EA code. A flame can be seen when I try to start it but the flame only last 1 or 2 seconds and then goes off.
Anybody can help? Thank you very much. Our home is very cold without heat.