When I click the link in the invitation email, I come to Invajo's homepage, why?

It can be due to several different things. Either way, you have sent a test invitation and this has no logic behind it and is only a visual test of how the invitation email looks like. It could also be because you have used an incorrect link or your booking page is not activated. You activate the page through the slider you find at the top right when you are logged in and working with the event.