Only registering one phone to CUCM

[fernando]

Hello!

I'm trying to register several Yealink W56H to our CUCM.
Phones find and join the base W60B correctly.
However, after configuring the phones to register to our CUCM, only one can be registered at time. If I register the first W56H with one account it registers, then I try with the second one and the result: "Register failed". If I unregister the first account and try again with the second one again, it succeeds.

Is it a problem of our CUCM configuration or we have to change anything in the account configuration in the web configuration page of the base?

The firmware version of the w60b base is 77.83.0.20
The firmware version of the w56h phones is 61.83.0.10
Our CUCM version is 10.5

Thanks in advance