Welcome to the forum @Nostalgator !
I know the prompt tells you that you are submitting a Pokestop, but you actually are submitting Wayspots to Niantic’s Lightship database. Only Wayspots that are alone in a level 17 S2 cell will be added to Pokemon Go. A good article about S2 cells is this one: https://pokemongohub.net/post/article/comprehensive-guide-s2-cells-pokemon-go/
You can check in the nomination screen while you are on site to see if a Wayspot already exists with the toggle in the map screen. Wayspots that are not being used for Pokemon Go will show as !
Sorry for the frustration, but hopefully this will help for the future!