The menu is not always shown on the smartphone
This means a lot of guests, but no registrations
What can I do to solve this?
Please leave some screenshot and your forum URL.
This problem doesn't have any relation to smarthons. The forum menu is gone.
You've changed the active theme and wpForo menu was disconnected to the menu location. Please navigate in Dashboard to Appearance > Menus admin page. Select the wpForo Navigation, then check/enable it for wpForo Menu location.
Also please read wpForo Menu Doc:
It still does not work on the mobile.
Will try again later