outwinded If you are sure that you completed all 4 steps (shown in screenshot) and the next mine still does not open, no new quest appears, then you might want to try some basic troubleshooting techniques. Log off, close game completely (close browser or App), clear cache, maybe even re-start PC or mobile device, re-open, log on again and see what happens. Last thing (on mobile) you could try is de- and re-installing the App, but make sure you have your Player ID written down before doing so.
If all fails you need to contact support directly
