Submit button not submitting when clicked

A new client of ours was kind enough to let us know the following via email: 

"hi there, I'm trying to send a query to one of your speakers and the form won't submit...."

When I asked how she would describe the exact experience she wrote:

"the issue was the 'submit' button on the 'make an inquiry' form, which didn't respond and submit the form, no matter how many times I clicked it."

Now, this is a serious issue to us - and potentially a deal breaker. How do you explain this and how do we know this doesn't happen to other people visiting our site and then leave in frustration that they can't even write a note to us?

Hi,

Thank you for letting us know about this.

I have tried to submit the jotform on your website to check if there is an issue or a conflict on the page, but everything went through properly.

You will see a submission with 'q' for name, please ignore it, this was my test submission.

I would suggest trying to make a submission yourself as well and let us know if you are able to replicate the issue.

I however presume that this was something on their side. Do you know what they have used to fill out your website? Might be that they did not have connection (if they used mobile device) at the moment that they clicked submit causing them to not be able to submit the message.

Best Regards,
Ben