I have a Multisite which I have tested new sites registration to work successfully. However, after I installed the WPMUDEV Domain Mapping plugin, not only was I not able to get the domain mapped successfully, every newly registered sites was unable to log into its Wordpress Admin Dashboard with the given password received.
I deactivated all plugins and retest the new site registration again. It works successfully until when I have the WPMUDEV Domain Mapping plugin registered. I do not think there is any plugin conflict as I am only using only WPMUDEV plugins such as New Blog Templates and Multisite Theme Manager.
To ascertain that my dedicated IP is working fine, I removed the WPMUDEV Domain Mapping plugin and installed Wordpress MU Domain Mapping plugin. This time everything works perfectly. Both the domain mapping as well as new sites registration.
I believe there is a bug with the WPMUDEV Domain Mapping Plugin.
For your info. :slight_frown: