Success message email not working

Hi guys, I’ve had a success message set up to be emailed across to someone when they get in touch via our online contact form, just to tell them we will be back in touch within a certain time frame. This was done through the ’emails & actions’ tab. I’ve just noticed recently that it is no longer sending. I’ve done tests from my own email and nothing is coming through. I’ve deactivated and then reactivated it again but still nothing. Can anyone help at all? Thanks so much

https://wordpress.org/plugins/ninja-forms/