Probably run out of water. Check header tank, drain some water from a drain cock and monitor tank. Cold feed may be blocked. Air bleed valve by HW cylinder may need venting.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local