Hi Douglas!
Thanks for getting in touch with us.
We are not aware of any problems regarding iOS 11.
I am getting blocked by Wordfence if I try to access your site. Probably because you are implementing some IP limitation. I think this could probably be related to the problem you are having in the iOS device.
I’d suggest you try disabling this IP limitation and see if it works. If it doesn’t, then it could be a conflict with your theme, another plugin or even some custom code. So, to make sure we are not dealing with a conflict, please go through the steps outlined in our Testing for Conflicts guide and see if you can reproduce the same issue under default conditions.
When coming back, please share with us your system information by following this guide > https://theeventscalendar.com/knowledgebase/sharing-sys-info/. We’ll see if there is anything strange that would indicate an error from there.
Thanks,
Victor