Site registration email not being sent

We are using Pro Sites on a network, but the activation email is not received upon registration. And some information like the email are missing from finalize page when a site is registered:
https://static.livechatinc.com/8801096/P50YPSFVE4/3b99a95ea9e2c339916f3afa5f839d1a/chat-530.PNG

Now we have 2 pending sites from the database that make it impossible to use their domains.

Any way we can fix the email activation issue and also remove the pending sites from database to allow new site creation with their domain?