This is being caused by using an old browser/phone that do not support the latest TLS standard.
Our security company recently had to disable TLS 1.0 in order to remain compliant with the PCI Security Standards Council:
Possibly you are trying to connect using TLS 1.0 which is no longer supported and is, therefore, causing this issue.
Try using the latest version of Chrome/Firefox on your device as a default browser.
Simply type in Chrome and it should work.
If that doesn't work, your device may not support >= TLS 1.1.

Here is a link how to check your TLS version: