Hey @Agent16A
"Versteckter Sandkasten"is in a occupied cell with “Tanzende Stangen” meaning it can’t show up as pokestop.
Cells:
Im not quite sure about the other one. Looks fine on the map in a onoccupied cell.
There might be a geoblock at this location by property owners preventing this wayspot becoming a pokestop which only staff can confirm.
Good luck