Why email took time to arrive or not working
Why email are not working
Please make sure if emails are not in spams or junks folders.
Why email took time to arrive
Email delay(arrival to the inbox) could be due to many reason. First of all this could be your email content. Some email providers like gmail take time to read content and decide either put it to spam or in inbox.
So your content should be strong, and don't write such kind of content which could be a suspicious.
This not related to theme because when any event trigger then it send email because php functions runs.
For testing purpose you can install this plugin https://wordpress.org/plugins/email-log/
When your click it will trigger an email and you can see on the back-end.