When you try to sign in to Skype for Business Online (formerly Lync Online) in Office 365 as an Office 365 Small Business customer who has a custom verified domain, you receive an error message that indicates that the server is temporarily unavailable.
Note Office 365 Small Business customers who have custom verified domains have those domains fully redelegated to Office 365. "Full domain redelegation" indicates a domain for which the name server (NS) resource records point to Office 365. Therefore, the Domain Name System (DNS) records that are required for Office 365 functionality are managed by Office 365.
To fix this problem, follow these steps:
Make sure that the NS resource records point to Office 365. To do this, use the Nslookup tool to query the name server records for your domain. The NS resource records should point to two of the following fully qualified domain names (FQDNs):
Note If the domain was recently configured for full domain redelegation, you should wait for 72 hours before you run a query.
If you still can’t sign in after the NS resource records have been changed, there may be a delay in publishing the Skype for Business Online DNS records. If this occurs, test the DNS records. To do this, follow these steps: