How do valentines entrance and message affects the plot?

Orsino's servant Valentine, whom Orsino sent to give his affections to Olivia, returns; Valentine was not allowed to speak directly to Olivia, but Olivia sent a message, via her handmaiden, that Olivia will continue to mourn her dead brother, and will neither allow Orsino to see her or to woo her. Orsino laments that Olivia does not hold the same deeply felt love that he professes to have.