If your wall-mounted boiler is not producing hot water and is making strange noises， there could be several reasons for this issue. Here are a few things that you can try to troubleshoot the problem:

1. Check the water pressure: Low water pressure can cause your boiler to stop producing hot water. Check the gauge on the boiler to determine if the water pressure is too low. If it is， you may need to adjust the pressure valve or add more water to the system.

2. Check the pilot light: If the pilot light has gone out or isn't working properly， your boiler may not be able to produce hot water. Follow the manufacturer's instructions to relight the pilot light.

3. Check for blockages: If the pipes or valves leading to the boiler are blocked， this can prevent hot water from reaching your taps. Check for any blockages and clear them out if possible.

4. Bleed the radiators: Sometimes， trapped air in the radiators can prevent hot water from circulating properly. Bleed the radiators to remove any trapped air.

If these troubleshooting steps don't solve the problem， it may be time to call in a professional to diagnose and repair the issue. A qualified plumber or heating engineer should be able to identify the problem and help you get your boiler working properly again.