[serusers] problem to register

[michael p]

hi

when i try to start my registration there is this error appears in the log 
diagnostic of my UAC:


4:32:06.8 Proxy slot #0 () - Failed to register! error-code: 401, msg: 
'Unauthorized'. Retry in 40 second(s). AOR: '<sip:michael at toto.koko.com>', 
proxy: toto.koko.com', firewall-proxy: 'F'.


i don't understand

thanks