Back button not working as intended

Not sure if this is the right place to post but...
The button which I presume is supposed to be a back button (the backwards arrow on top left of screen) doesn’t seem to have any functionality? It doesn’t do anything when I click it.
The button which I presume is supposed to be a back button (the backwards arrow on top left of screen) doesn’t seem to have any functionality? It doesn’t do anything when I click it.