First thing I'd check is polarity. Has the meter installer reversed the polarity, either making it wrong now or making it right when it was wrong before? This is the only thing I can think of that could conceivably cause immediate RCD tripping after a meter change
Wouldn't cause tripping in itself, of course, but would, if there was a particular common, pre existing, serious fault..
Any idea what sort of fault would cause an RCD to trip with a polarity reversal ?