Unity 3D UI Buttons not working on mobile device
<p>For few days I'm encountering a strange problem that my buttons don't work when I build and run my game on the mobile device even though they work just fine in the editor. What's even more surprising is only the buttons that are placed for the actual gameplay level don't work. All buttons prior to that level on the menu screens and work.</p>

<p>This problem only started occurring a couple of days ago before that there was no such thing. I worked around this problem by first building the game with Orientation 'Landscape Left' and then again building it with 'Auto Rotation' and checking the 'Landscape Left' checkbox in the player settings or vice versa. That will make buttons work again on the mobile device. But today when I build a second level I found that this problem also occur on Second level even though I made it to work on first level.</p>

<p>It's driving me crazy, I don't know what to do. The only difference between Menu and gameplay level is that on the gameplay level I'm placing objects using some objects using Instantiate.</p>

<p>Yes, I have checked I have placed the EventSYstem on the level and GraphicsRaycaster script on the canvas.
Any ideas?</p>