Hi Fanias,
Just a guess on my part
SEROUT2 CIVP,CIVS,[$FE,$FE,CIVA,$E0,$14,$01,$FD] ' Send this to the radio to read Audio SETTING - WORKS !!!

CIVA is uppercase

SEROUT2 CIVP,CIVS,[$FE,$FE,civa,$E0,$14,$01,$f3,$f4,$FD] ' Send this to the radio for NEW VOLUME setting - NOT WORKING

civa is lowercase

I am GUESSING, since I do not know what the radio does but uppercase and lowercase letters are different numbers as all characters are numbers . . .
also same for F vs f