In some cases, you might not be able to access Audiocodes after resetting the unit. This could happen if you are running a DHCP server that response to bootp request.
Audiocodes, whether you have assigned an IP or it is set to DHCP, will send a bootP request…
I have seen this happens when pfsense is used as firewall. Pfsense will assign an IP to any unit that requests bootP.