Why an Image Prefab Event Trigger does not working...

I have both text box prefab and image prefab shown on screen which need to detect point enter and exit. I have written a c# script to handle both enter and exit, and have attached it to both prefabs. I added Event Trigger (Pointer Enter and Pointer Exit) to both prefabs. My problem is, the text box works fine but the image prefab instance can not detect pointer enter. Any clue why is it?

I tried to add a box collider to the image prefab. It now recognize the pointer enter and exit, but I still need to handle “PointerClick” event, but it does not respond to my mouse click. Still need help! Thanks a million!