The location is in /mnt/mmc/asterisk/voicemail/default/<extension number>/

The unavailable message should be named as unavail.wav and the busy message should be named as busy.wav.
The audio file format must be WAV format in 16-Bit PCM encoded, 8 KHz and mono.

edit /etc/asterisk/rc.conf

IF=eth0 IF=eth1 IFL=eth0 TO IFL=eth1 (Default setting)
IF=eth0 IF=eth1 IFL=eth1 TO IFL=eth0 (LAN port becomes WAN port and the WAN port becomes LAN port)
also the rc_auto.conf pls check

cd /etc/zycoo-gui
./setdefault.sh

check /var/log
du -sh *
rm message

asterisk -vvvr

core reload

You need to access the IP PBX via SSH and issue command:
crontab -e
and at the bottom of the file you need to add a new line:
0 6 * * * /sbin/reboot
Then it will reboot the IP PBX every day at 6:00 am automatically.

Our IP PBX can support Caller ID signaling Bellcore FSK, DTMF, V23 and V23 Japan. Please ask your Telco what signaling is applied on the PSTN lines and then configure Caller ID signaling on web page Advanced-->Global Analog Settings.