I tried to remove one of the card and modify the zaptel.conf and zapata.conf and it works with either of the cards.
The error only happens with boths cards installed in one server. I also tried to delete file zapata_additional.conf and remove the line #include zapata_additional.conf in zapata.conf.
[
[email protected] ~]# ztcfg -vv
Zaptel Configuration
======================
SPAN 1: CCS/ AMI Build-out: 0 db (CSU)/0-133 feet (DSX-1)
SPAN 2: CCS/ AMI Build-out: 0 db (CSU)/0-133 feet (DSX-1)
SPAN 3: CCS/ AMI Build-out: 0 db (CSU)/0-133 feet (DSX-1)
SPAN 4: CCS/ AMI Build-out: 0 db (CSU)/0-133 feet (DSX-1)
Channel map:
Channel 02: FXS Loopstart (Default) (Slaves: 02)
Channel 03: FXS Loopstart (Default) (Slaves: 03)
Channel 04: FXS Loopstart (Default) (Slaves: 04)
Channel 05: Clear channel (Default) (Slaves: 05)
Channel 06: Clear channel (Default) (Slaves: 06)
Channel 07: D-channel (Default) (Slaves: 07)
Channel 08: Clear channel (Default) (Slaves: 08)
Channel 09: Clear channel (Default) (Slaves: 09)
Channel 10: D-channel (Default) (Slaves: 10)
Channel 11: Clear channel (Default) (Slaves: 11)
Channel 12: Clear channel (Default) (Slaves: 12)
Channel 13: D-channel (Default) (Slaves: 13)
Channel 14: Clear channel (Default) (Slaves: 14)
Channel 15: Clear channel (Default) (Slaves: 15)
Channel 16: D-channel (Default) (Slaves: 16)
15 channels configured.
ZT_SPANCONFIG failed on span 6: No such device or address (6)
[
[email protected] ~]# tail /var/log/asterisk/full
Nov 13 14:46:05 WARNING[5460] pbx.c: Context 'ivr-2' tries includes nonexistent context 'ivr-2-custom'
Nov 13 14:46:05 WARNING[5460] pbx.c: Context 'ivr-2' tries includes nonexistent context 'ext-findmefollow'
Nov 13 14:46:05 WARNING[5460] pbx.c: Context 'app-callwaiting-cwon' tries includes nonexistent context 'app-callwaiting-cwon-custom'
Nov 13 14:46:05 WARNING[5460] pbx.c: Context 'app-callwaiting-cwoff' tries includes nonexistent context 'app-callwaiting-cwoff-custom'
Nov 13 14:46:05 WARNING[5460] chan_zap.c: Unable to specify channel 1: No such device or address
Nov 13 14:46:05 ERROR[5460] chan_zap.c: Unable to open channel 1: No such device or address
here = 0, tmp->channel = 1, channel = 1
Nov 13 14:46:05 ERROR[5460] chan_zap.c: Unable to register channel '1'
Nov 13 14:46:05 WARNING[5460] loader.c: chan_zap.so: load_module failed, returning -1
Nov 13 14:46:05 WARNING[5460] loader.c: Loading module chan_zap.so failed!