Hello. I have an error 24 on my smeg dishwasher,model cw511mdaus-2. what is the error?how to reset machine,thank you. cheers Andrew

This is a commercial unit it error codes are different
Er 24 Boiler temperature probe Boiler temperature probe disconnected or not working malfunction
this is in the user manual

That isn't a Smeg Error code. Are you sure it isn't E4?

CODE: E4
PROBLEM: Faulty Temperature Sensor
FIX: The temperature sensor monitors the temperature of the water in your dishwasher. Check the sensor itself and the wiring and connections to it and repair or replace as necessary.

https://www.google.com/search?q=smeg+cw511mdaus-2+error+24

I am Andrew as well Andrew :>)