Hi BlueBerry88,
Checking the DNS record settings is a troubleshooting step if the Lync client cannot connect the server. You can change another network environment and test it, for example, log into Lync client at home or from a public Wi-Fi network.
In addition, since the original post of this thread is not related to Lync sign-in issue, in this situation I'd like to suggest you create a new thread with detailed information about the Lync connectivity issue. This will help us troubleshot the issue more effectively.
Thanks,
Bourne Zhang