1. If you are unable to sign in, try from another browser. If on a laptop, then Google chrome is the preferred browser or latest Edge browser
2. If you are trying from a Mobile or Tablet use Chrome (Android based).
3. If you are using iPhone or iPad, the preferred browser is Safari (default browser).
4. If still not working try to clear the cache and reset cookies.
5. If the above are not working, Switch to a different network. For e.g if you are on WiFi, then switch to 4G and try again.
6. If steps <1> to <5> are not working try going into Incognito Tab on the browser.
The easiest way to open an Incognito window is with the keyboard shortcut combination Ctrl-Shift-N (Windows).