1. Thanks for sharing the screenshot. I see that the reply was added to a review that was left directly on a product page. Our plugin is able to send email notification about replies only for reviews that were left via aggregated review forms.
Unfortunately, the plugin cannot send email notifications for replies to reviews left directly on the product page. We do not have permission to send emails to customers in this case because they did not accept terms and conditions.
2. Caching plugins are tricky. They can break other plugins or entire websites. So, if there is any problem, the first step of troubleshooting is always to disable the caching plugin.
If it works fine now, you are welcome to enable the caching plugin. If you don’t notice any problems after that, it should be ok to keep the caching plugin enabled.