Jan

Please provide more details.

But taking a guess:-

If everything is fine at other resolutions I suspect you have imported from an earlier version. For reasons I do not understand the mobile resolution page content is frequently hidden.

On every page where there is no content at mobile resolution, go to step 4 page and select responsive settings. Go to the resoluton above mobile (by default 720px)

Select show/hide for lower resolutions and "unhide" the cells