Avaya 9640 SIP (or similar) with UCM6204 does not work


Hi everyone, I’m new to this forum and I hope you can help me.
My problem and I am blocked: :Cara cansada:
I have a UCM6204 that we use for tests, we want to connect some Avaya 9640 termianles, we have updated the frimware of the phone to the version that Avaya indicates in SIP 2.6.17 mode.
When I configure the phone with the SIP server parameters, addresses, etc. I can ping without problems from the phone to the PBX, but when loging can not. Indicates Adquiring service.
Someone has been able to run an Avaya in SIP on a UCM64xx.

Thank you.