Unable to map new domains after upgrade to 3.1 of Domain Mapping plugin

I'm trying to map a new site I created on my multisite since upgrading to version 3.1 of the plugin but I'm not having any luck. I previously was able to map domains but after the upgrade I noticed that the domains I had previously mapped no longer appeared in the list (under Tools -> Domain Mapping). I thought that was strange especially since the domains still actually did work. I added them again just to be safe and didn't think anything of it.

However, now when I try to add any new sites (or even a new domain to an existing site) that wasn't in the list before the upgrade, it doesn't seem to work. I even tried deleting the plugin and reinstalled it but no luck with that either. I have tried with more than one site and more than one domain and no luck.

Is there a bug or something else I maybe missing?