Hold down Ctrl and click the Reload button.
Or, Hold down Ctrl and press F5.
just open the Chrome Dev Tools by pressing F12. Once the chrome dev tools are open, just right click on the refresh button and a menu will drop down.
If you've logged in on another browser and try to navigate on your original, it prompts you because your session was probably killed. Sometimes it prompts you for a login to try to redirect you. Sometimes that doesn't work, I found. Just reload the login page itself and it should work just fine.
@Danger-Noodle while on a mobile device and maybe tablet the site turns into responsive mode and the composer is supposed to take over the screen in order to give you the most real estate due to on screen keyboard.