I think your latest software isn’t. I seem to remember renaming the variable to avoid this, it was quite a while ago - yes: “Version 2.1.2 7/8/2021 ‘assumedACVoltage’ was ‘assumedVrms’ (name conflict in some sketches).”
So I suggest you get the real latest version from the emonLibCM topic on the forum. That should solve your problem. You should always go there for the latest version.