Same/similar issue as here:

https://social.technet.microsoft.com/forums/lync/en-US/5ddd7fd0-a31d-44a1-8b0c-8a1e2cd89530/lync-client-ios-the-server-name-is-incorrect-using-autodiscover

Any ideas?iOS 8.3 and Lync version 5.7

Are you connecting internally or externally?  Does it work via other mobile clients?  If you navigate to https://lyncdiscover.sipdomain.com and you open the returned .json in the mobile client, do you see only external server names or are any internal? 

Hi Martin Bergstrom,

 

In addition, please check the certificate and make sure the related FQDN is included in the server certificate.

 

Best regards,

Eric