ACKUL,
A few questions first:
Q1: Are the TA5000 FXS ports on a xPON ONT or a VDSL Combo card?
Q2: Are you using IP addresses or FQDN for the SIP server and Registrar server?
Q3: Is the IP-Host obtaining an IP address?
Q4: North of the TA5000 is the VoIP VLAN switched / routed to the SIP Server?
Q5: Is your Voice User provisioning using the correct auth-name and password values?
Provide a "show run" of your voice configuration.
Regards,
BMULLAR