I followed the instructions and pressed ‘about smarttings’ for 5 seconds or more, but the develop mode did not appear. I am using iOS.
Did you notice if the field highlight disappears and then scroll down to find it at the bottom of that screen?
On my iOS device… when I press on the field, it is highlighted a darker color and switches to a white background after 5 seconds. I then need to scroll down to to see the developer field at the bottom.
Yes, I noticed that the highlight disappeared after 5 seconds, but the develop mode did not appear.