As per The Metropolitan Opera:
"Rolando Villazón is still struggling with acute laryngitis. In order to
give himself the rest he needs to make a full recovery, his doctor has
advised him to withdraw from the remaining performances of L’Elisir
d’Amore. He has canceled performances on April 8, 11, 15, and 18."
Barry Banks will sing Nemorino on April 8, Joseph Calleja will sing on April 22, while the remaining performances on April 11, 15 & 18 "will be announced soon".