Hi @Caitlin_E_Howley, welcome to the Community Forum and sorry for the trouble!
In order to best assist you, could you please confirm if you are receiving an error message or if you are able to send the email invites but the users cannot accept it?
If the new members are not receiving the email invites, unfortunately we don’t have the tools in the forum to troubleshoot this further. Please advise them to contact our support team: How to contact our Support Team ✉.
I hope this helps! Let me know if you have any follow-up questions!