[SR-Users] I_SCSCF_select function dont return the next SCSCF in IMS network!!!

Hello, Today i have a strange problem in IMS network. All nodes (pcscf,icscf,scscf and hss) are configured in independent server. My domain is default(open-ims.test) Now when i want to register bob(a)open-ims.test, I get this error from ICSCF: 500 Error in request. When i saw the log files, i found the icscf could not found the next node(scscf) in registration path. As i defined prefered scscf_uri in configuration file, Why the icscf, could not found the scscf? The dns server works correctly and i have ping of scscf.open-ims.test from icscf node. When i trace the diameter packets, the icscf connect to hss successfully but dont send UAR to hss while registration proccess!! It's strange. Please let me know why i have this problem, Thanks With Regards. -- --Mojtaba Esfandiari.S