Has something happened to rg2sc?
I've just noticed this over the past week after updating to the latest 2.80 version. The $rg2sc function doesn't appear to be writing anything out to the ITUNNORM tag. I invoke it using the action that garym kindly posted here.
Looking back through my collection, I suspect the problem began with the 2.79 upgrade, but I've only just noticed it in the past couple of days.
[Edit]
I did some experiments and found the problem isn't with the $rg2sc function, which works fine when called directly. Instead, something's changed with the control logic for action scripts. garym's combined action uses simple logic on the file extension to detemine how to tag the soundcheck info, and this now seems to be failing, whereas it worked fine before:
[#2]
T=5
F=ITUNNORM
1=$if($eql(%_extension%,m4a),$rg2sc(%REPLAYGAIN_ALBUM_GAIN%),)
does nothing when run on a .m4a file.
Calling the function directly works however:
[#0]
T=5
F=ITUNNORM
1=$rg2sc(%REPLAYGAIN_ALBUM_GAIN%)