From the debugs, it seems like the phone is indeed getting the config file.
Oct 17 06:08:17.029: TFTP: Looking for SEPB07D47C131AA.cnf.xml
Oct 17 06:08:17.033: TFTP: Opened flash:/its/vrf1/SEPB07D47C131AA.cnf.xml, fd 4, size 1534 for process 62
Oct 17 06:08:17.041: TFTP: Finished flash:/its/vrf1/SEPB07D47C131AA.cnf.xml, time 00:00:00 for process 62
The next step is the phone should send a register message to the CME IP :172.16.252.123. You can check this by taking a packet capture from the phone. Also can you provide the "show run".
Can you provide the below debug after resetting the phone once:
debug tftp events
debug sccp messages
debug ephone register
You have mentioned that you are able to register 3 other models. Are they sccp or sip ?
sThose are SIP models. debug .... Oct 19 07:14:10.662: TFTP: Looking for CTLSEPB07D47C131AA.tlv Oct 19 07:14:10.778: TFTP: Looking for SEPB07D47C131AA.cnf.xml Oct 19 07:14:10.778: TFTP: Opened flash:/its/vrf1/SEPB07D47C131AA.cnf.xml, fd 10, size 1529 for process 62 Oct 19 07:14:10.786: TFTP: Finished flash:/its/vrf1/SEPB07D47C131AA.cnf.xml, time 00:00:00 for process 62ephone-3 Mac:B07D.47C1.31AA TCP socket:[-1] activeLine:0 whisperLine:0 UNREGISTERED mediaActive:0 whisper_mediaActive:0 startMedia:0 offhook:0 ringing:0 reset:0 reset_sent:0 paging 0 debug:0 caps:0 IP:0.0.0.0* 0 Unknown 0 keepalive 0 max_line 0 available_line 0 button 1: cw:1 ccw:(0) dn 3 number 1003 CH1 DOWN Preferred Codec: g711ulaw
Can you try deleting the ITL/CTL on the phone if any using the below procedure (It will be similar for 6901 phone but options might differ) and if the issue persists, let me know what you see in the status message on the phone.
you could follow the below steps and do a factory reset. But pls make sure that you have a valid DHCP in your network. Else the phone wont come up.