Thank you for your response and trying to help me!
I was using the most recent version before the last one. Today I reinstalled the plugin so we upgraded to the latest version and I have followed the prompts on clearing the page cache every time I make any sort of change.
After re-installation I can add in a few email addresses and it works and sends out emails but if I add in the whole list which is about 18 people then it stops working.
I have tried both copy and pasting in the list from the downloaded csv and manually typing the addresses in. Neither method solved the problem.
Any ideas? Thank you.