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I checked your jotform http://www.jotform.com/51413937669162 and I was able to trace the possible cause of issue.
Please review also our user guide on Send-Notifications-to-Multiple-Recipients
There's a limit of 10 recipients per notifiers and 2 for autoresponders. So, you'd need to create additional notifications (containing the same information) if you wish to send the message to more than 10 people.
I can see that you had more than the allowed 10 recipient setup on the Notifiers. This could be causing the issue.
Also, you can check if emails were bounce listed. You can ublock them by following this user guide:
Hope this help. Please let us know if issue persist.