[Serusers] Server does not see the REGISTER message

Hello, I have a problem with SER. The server starts successfully: +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Mar 3 12:14:11 localhost ser: WARNING: could not rev. resolve 159.199.75.160 Mar 3 12:14:11 localhost ser: Listening on Mar 3 12:14:11 localhost ser: 127.0.0.1 [127.0.0.1]:5060 Mar 3 12:14:11 localhost ser: 159.199.75.160 [159.199.75.160]:5060 Mar 3 12:14:11 localhost ser: Aliases: localhost:5060 localhost.localdomain:5060 Mar 3 12:14:11 localhost ser: Listening on Mar 3 12:14:11 localhost ser: 127.0.0.1 [127.0.0.1]:5060 Mar 3 12:14:11 localhost ser: 159.199.75.160 [159.199.75.160]:5060 Mar 3 12:14:11 localhost ser: Aliases: localhost:5060 localhost.localdomain:5060 Mar 3 12:14:11 localhost ser: Listening on Mar 3 12:14:11 localhost ser: 127.0.0.1 [127.0.0.1]:5060 Mar 3 12:14:11 localhost ser: 159.199.75.160 [159.199.75.160]:5060 Mar 3 12:14:11 localhost ser: Aliases: localhost:5060 localhost.localdomain:5060 Mar 3 12:14:11 localhost ser: Iniciación de ser succeeded +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ But when I send him a REGISTER message, the server do nothing. My SIP_DOMAIN=localhost, and the REGISTER message arrives to the PC where the server is running. I have not changed the ser.cfg which becomes with the installation. Can anybody help me?