Skype Business 2015 problem child domain

Hello,

I have parent domain : contoso.com and one child domaine : ukie.contoso.com
First, I can't create user from control panel for users located in child domain

Error: “Active Directory operation failed on “Domain Controller”. You cannot retry this operation: “Insufficient access rights to perform the operation”.

Then I can create the user with powershell.

When I try to connect my user on skype client, I have this error: You didn’t get signed in. It might be your sign-in address or logon credentials, so try those again. If that doesn’t work, contact your support team.

And error from log (attached file)

And here result when I try to test connectivity:

Test-CsRegistration -targetfqdn lyncpoolfe01.contoso.com -usercredential $cred1 -usersipaddress sip:ccharles@contoso.com

Target Fqdn   : lyncpoolfe01.contoso.com
Result        : Failure
Latency       : 00:00:00.0009741
Error Message : The log on was denied. Check that the proper credentials are
                being used and the account is active.
                Inner Exception:NegotiateSecurityAssociation failed, error:
                -2146893044

Diagnosis     :

Select allOpen in new window

Why my child users can't connect to skype on parent domain? Should I perform actions, like prepare ad or forest for this child domain?

Thanks in advance
SkypeLog.txt