You must have at least a 4-heart friendship level with an NPC for them to accept your invitation.
It is difficult to get a partner in the first year. Players often target Shane or Haley by gifting their favorites (like daffodils or beer) consistently and talking to them daily. Flower Dance
Purchase the Rarecrow #5 and the Tub o' Flowers recipe from Pierre's booth during the event. 🎨 Creative & Educational Activities You must have at least a 4-heart friendship
Dance with a bachelor or bachelorette to gain friendship points. Flower Dance