Audi A4 2017 Engine speed governing.

[PHB]

I am getting a warning "engine speed governing" displaying on my screen. It states I must not increase the revs above 2500rpm. It frequently occurs when I am accelerating which is a problem as I lose power, it is as if the speed limiter has come in. This started after I had the water pump and thermostat changed which the garage does not believe would be an issue and the garage can not find any fault codes.  In the manual it stated this is to stop the engine overheating but the temperature is normal and sometimes the engine is cold as I have only traveled a few miles. Has anyone got any ideas what could cause this fault.