Some doors stay closed because you knocked too loudly. Try the side entrance with a better plan.

A no is sometimes about the approach rather than about you. Turning up demanding, over eager or at the wrong moment makes people defensive before they have considered the actual request, and then the answer hardens. The same ask, made differently, often gets a different reception. That is not a trick, it is just how people respond to pressure.

Take the thing you were refused and change one variable before trying again. A different person, a smaller version of the request, a quieter message rather than a public one. Give it a few weeks, then go back without mentioning the first attempt.