Next Fails on IOS Browsers

I have found similar issues on this forum, and have tried the solutions offered therein. After clearing my WP server cache, as well as the local cache and cookies in each browser named below, I am unable to proceed from the first step of the form to the second. I have performed the same test on an iPhone and an iPad (clearing all caches each time). In Safari, clicking ‘Next’ does not advance the form, but displays the form submit success message (the form isn’t actually sent). In Brave Browser (Chromium), clicking ‘Next’ advances the form, but the next page displays “Please fill out the form on the previous page”, with no form fields visible. To be clear, these issues only arise on mobile devices. The multi-step form works perfectly on a desktop.