I started having same problem yesterday after I installed WordPress HTTPS (SSL) to fully secure my site with external links such as google fonts, etc.
But sooner than later did I realize my site started breaking apart. I spent over 15 hours to uninstall and reinstall wordpress latest version to flush out the problem also removed the plugin but my site is still broken.
My site is not working all of sudden on all the browsers the same way, IE, Chrome and Safari.
However, the main problem I start having is yesterday evening 5pm CST where my site url stopped working when I key saintll.com but it doesn't open anything. Then I put https://saintll.com to make it work. This is the only temporary or dirty workaround I have and this is a freelance I am doing for a giant company in U.K and it is a huge impact.
All I want is the site should work if I key saintll.com and that should redirect url to https://saintll.com without me having to key https:// myself. Same thing for wp-admin, it should take me to dashboard when I key in saintll.com/wp-admin and be redirected automatically to https://saintll.com/wp-admin. Currently, https://saintll.com/wp-admin isn't working properly either. Keeps kicking me out.
It should work like before, whether you key:
http://saintll.com -> redirects to https://saintll.com
http://www.saintll.com -> redirects to https://saintll.com
Similarly for wp-admin it should work as saintll.com/wp-admin
Waiting for your reply and solution to fix this.