Seek the Signs of Allah
How do we know that Allah SWT exists? The first and foremost requirement for a person to become a Muslim is to believe whole-heartedly that Allah SWT exists. Allah SWT, the one and only God.
Nevertheless, He cannot be seen by a human-or any living creature, for that matter. In simpler words, Allah SWT is invisible. He was, is, and will be invisible for the rest the world;s existence until the day when the universe comes to and end.