Your boiler has detected a general internal error and has safely shut itself down to prevent damage, meaning you currently have no heating or hot water.

Internal fault (Reset required)

What causes this fault?

A solid red light indicates that the boiler's internal safety system has detected a generic malfunction, preventing it from firing up. This is often caused by a failure in the ignition process or a breakdown in communication between the main control board and vital components like the gas valve. While a simple reset may temporarily clear it, the fault usually points to a failing part that is no longer operating within safe limits.