Website log in

Try double clicking the Home button or swipe up from the bottom of the screen and swipe Safari upwards. Go to Settings/Safari and clear History and Website Data. Open Safari and test.

Safari - Clear the history and cookies on your iPhone, iPad, or iPod touch

Safari website data on your iPhone or iPad - How to clear

Do you have access to another WiFi network where you can try? That has worked for several people.

Try a restart.

Restart your iPhone, iPad, or iPod touch

Try a forced restart.

Reset Device

If necessary

Hard reset

Do a backup and try a factory reset. Then restore from your backup.

Restore to Factory setting

Backup - Restore your device from an iCloud or iTunes backup

Similar thing happend with me. i opened https://twitter.com

both are showing you can't access to this site from safari.. before a day everything was fine now showing this what to do now and how can i resolve this issue?

[Link Edited by Moderator]

Have you tried what I posted above?