I had a similar problem after installing the Dynamic Enviromment Sound MOD.
Not only my radio guy was silent, also my navigator, when asked to determine depth under kiel, happily turned to his map, gently caressed it and said...nothing.
My LI did not report the current depth and my radio man did not say a word ouside the dialog box.
I resolved this issue by installing everything related to sound first and THEN applied the MFCM and MCCD MODs, which i find absolutely essential.
Then...loading....waiting...DANG! "contact. freighter. far away."
I've never been sp happy to hear little Bennos voice
