See or detect. Let's say you refuse the mark, and walk into a store and want to buy something. How can they tell if you do not have the mark?
I pay all my bills and buy all my food etc online.
What do you do?
There is an awful lot of speculation being imposed on the text, which should be understood for what it actually says, not what people imagine it might mean.
No where does Revelation say the mark is visible.