Could you provide us the error message if possible?
Except the DNS records, you may also be able to purchase lower-cost hardware load balancers than if you used the hardware load balancers for all types of traffic. You should use load balancers that have passed interoperability qualification testing with Skype for Business Server. For details about load balancer interoperability testing, see Lync Server 2010 Load Balancer Partners.
Besides, check if there is any related error message in Lync server event viewer in Skype for Business front end servers.
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