Usually this security warning may occur on any devices, on any browser stating that: “There are problems with the security certificate for this site”. And no matter what button you’ll press the warning will appear again.
How to fix it
The solution is very simple, the “security certificate” of a website is limited in time and to verify whether it’s actual or not the system automatically tries to match the expiration date with the date you have on your device. So the first thing you need to check, is if your device matches the “date&time” we actually have. And if its wrong, update it.
On Android go to Settings > Date & Time, to change the date use Set date, to change the time use Set time, also check if you have the nearest Time Zone selected.
On iOS go to Settings > General > Date & Time, check if you have the nearest Time Zone (for this turn off Set Automatically), then update Date & Time.
Now after the browser gets restarted, the warning shouldn’t bother you any more.