What were some of the problems Christopher Columbus encountered with his proposal to King John II of Portugal to sponsor his voyage?

Answer 1

First of all, the commitee appointed by the King to study Columbus' proposal discovered that Columbus was grossly miscalculating and underestimating the distance to China: the geographic location on the globe of China was well-known to the Portuguese through their earlier travels by the eastward route. So it advised the King not to go along with Columbus' plans. Columbus himself had asked for 10% of everything that was to come out of his discoveries, which also did not sit well with the King.

Finally, word had come in to the King that the eastern route had in the meantime been discovered to be feasible. The King then was no longer interested in trying a western route.