WordPress Site w/SSL will not Connect IOS (iPhone or iPad)

I have a wordpress using Bingle theme. The site is using a SSL. The site works fine on Windows (New Edge, Chrome and Firefox). It works fine on Android (Chrome). It will not load on iOS (iPhone 7 and iPad Air) with Safari, Chrome or Firefox. The progress bar starts but fails.

I created a duplicate site on new Plesk server and configured SSL on it https://rapidtestingcentre.co.uk/. The development site has the same issue with not working on SSL.

Troubleshooting:
1. I have disabled all plugins
2. I switched themes
3. I checked the Certificate and it’s showing green sign.

Please suggest is there any update in theme or any security code patch? I would appreciate any help.

Thanks