I keep this reply ready for folks looking for their “PokeStop”:
I know the prompt tells you that you are submitting a “Pokestop” but you are actually submitting a Wayspot to the database. The Wayspot can only become a Pokestop or gym if it is alone in a level 17 S2 cell. This is a good article about S2 cells and PoGo: https://pokemongohub.net/post/article/comprehensive-guide-s2-cells-pokemon-go/
If you would like to leave the title and location, someone here can check if this is the issue. But do be aware this is a public forum if you would rather not reveal your location.