Hello,
After debugging, I discovered that the issue with my "OnMouseDown" not working was originating from the inputTouch script. I resolved it by unchecking the "useMouse" option in the inspector.
Attachment Of Script.
https://drive.google.com/file/d/1woLIwrZoJqwMJ_4U_Ky6CiHDaMbhc6D1/view?usp=sharing