Check the phones, make sure they have a system forward path to voice mail and that the path is yes for RING NO ANSWER and CO TRANSFER/AA/VM (SYSTEM/DEVICES/PHONES/<EXT>/FORWARDING PATHS). Also make sure SYS FWD is not disabled (SYSTEM/PHONE RELATED INFO/FLAGS/SYSTEM FORWARDING, ext should be in list). Make sure each ext does have a voice mail account. Make sure SYS FWD INITIATE timer is shorter than TRANSFER - VOICE PROCESSOR (SYSTEM/TIMERS AND LIMITS).
If a live person transfers a call does it go to VM box if unanswered?