[SR-Users] Kamailio challenges repeatedly

I am trying to register with Kamailio server from my custom endpoint. I have below call flows Register -> 401 Register -> 401 When I saw Kamailio log, I do not see any error. Looks auth response is fine. Then why 401 repeatedly. Log is given blow. Please guide to fix this issue. Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: auth_db [authorize.c:208]: get_ha1(): HA1 string calculated: 8749f9da135d71526725a337008df1d5 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: auth [api.c:211]: auth_check_response(): check_response: Our result = '4aa70d676021329550b3d17e17238fac' Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: auth [api.c:218]: auth_check_response(): check_response: Authorization is OK Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:81]: db_free_columns(): freeing 1 columns Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:85]: db_free_columns(): freeing RES_NAMES[0] at 0x7f8a24d5e1d0 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:94]: db_free_columns(): freeing result names at 0x7f8a24d7ceb0 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:99]: db_free_columns(): freeing result types at 0x7f8a24d7cef0 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:54]: db_free_rows(): freeing 1 rows Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_row.c:97]: db_free_row(): freeing row values at 0x7f8a24d5e260 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:62]: db_free_rows(): freeing rows at 0x7f8a24d5e218 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [db_res.c:136]: db_free_result(): freeing result set at 0x7f8a24d7ce18 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: auth [challenge.c:127]: get_challenge_hf(): build_challenge_hf: realm='10.10.64.125' Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: auth [challenge.c:269]: get_challenge_hf(): auth: 'WWW-Authenticate: Digest realm="10.10.64.125", nonce="VfbImFX2x2yEeE8kEuL2IXqW2TgKu+eC"#015#012' Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: sl [sl.c:296]: send_reply(): reply in stateless mode (sl) Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [msg_translator.c:206]: check_via_address(): check_via_address(10.3.2.18, 10.3.2.18, 0) Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [tcp_main.c:2283]: tcpconn_send_put(): tcp_send: send from reader (2650 (9)), reusing fd Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [tcp_main.c:2518]: tcpconn_do_send(): tcp_send: sending... Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [tcp_main.c:2552]: tcpconn_do_send(): tcp_send: after real write: c= 0x7f8a1c5dbe78 n=445 fd=9 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [tcp_main.c:2553]: tcpconn_do_send(): tcp_send: buf=#012SIP/2.0 401 Unauthorized#015#012Via: SIP/2.0/TCP 10.3.2.18:6970;branch=z9hG4bK1875333638#015#012From: < sip:262099922700000@10.10.64.125;user=phone>;tag=209355482#015#012To: < sip:+499922700000@10.10.64.125;user=phone>;tag=8345fd11d20ec1ca026994bf51313cb0.a2c6#015#012Call-ID: 1340939517(a)10.10.64.125#015#012CSeq: 3 REGISTER#015#012WWW-Authenticate: Digest realm="10.10.64.125", nonce="VfbImFX2x2yEeE8kEuL2IXqW2TgKu+eC"#015#012Server: kamailio (4.2.5 (x86_64/linux))#015#012Content-Length: 0#015#012#015#012 Sep 14 18:41:08 necs107 kamailio[2650]: DEBUG: <core> [usr_avp.c:643]: destroy_avp_list(): DEBUG:destroy_avp_list: destroying list (nil) Sep 14 18:41:08 necs107 kamailio[2650]: message repeated 5 times: [ DEBUG: <core> [usr_avp.c:643]: destroy_avp_list(): DEBUG:destroy_avp_list: destroying list (nil)]