I was using WordPress Multisite for multiple TLDs.
Example:
- domain.com
- another-domain.org
- sample-domain.net
The primary site was domain.com
which was a valid registered domain name with proper DNS resolution.
another-domain.org
and sample-domain.net
had both expired domain name registrations. A/K/A – The DNS wasn’t resolving properly.
If you’ve got a WordPress Multisite setup similarly to mine, where you have multiple TLD’s in your network. Consider firstly verifying that all of the domains in your network are indeed still valid and registered.
ping domain.com
or
whois domain.com
If all of the domain names in your network are indeed registered, double check your DNS records to insure proper configuration.
Please also remember that in most cases, altering DNS records can sometimes takes upwards of 72 hours to fully propagate world-wide.
Solution for me was: Validate DNS records.
P.S. Another idea may include checking your firewall configuration(s).