This is probably due to the proximity rules and Pokemon Go that uses S2 Cells.
More details Why an accepted Wayspot may not be used in Pokemon Go (S2 cells and Pokemon Go)
Just an extra note, if by this comment you mean that you nominated the “Swings”, “Slide”, “Climbing Frame” etc all as different nominations then this is against criteria and everything apart from the 1st one should have been rejected. A “Playground” should be 1 nominations.
If there are other parts of the park such as Basketball court, picnic area then these can be nominated separately.
Good luck