Betel palm plants start bearing fruits after 4-6 years of age. If it is too young, it may not produce fruits. There may be several reasons that betel palm fails to product fruits. I would like highlight two; insufficient water and nutrient deficiencies. During summer time, you should have a ground cover with straws at the base of the betel palm. For nutrients, you can apply amounium sulphate fertilizer after the weeding actvitiy.

Sorry for mistaken with betel palm. Acutally, the nature of theose plants are similiar. Can you also check whether there are pests like spider mites or scale insects. Also do weeding near the plants as the weeds are competiting with our plants and getting the nutrients.