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 of the world's existence until the day when the universe comes to an end.