From Evenpro:

The Iron Maiden Concert at HSBC ARENA has been postponed to Monday, March, 28th due to technical problems with the barricade provided in front of the stage.

This decision was taken by HSBC ARENA in agreement with the band’s staff, because it’s their priority not to put fans’ safety in risk.
Iron Maiden will stay in Rio de Janeiro one more day to be able to make the show and not leave Rio de Janeiro out of this leg of The Final Frontier Tour.
All the fans at tonight (Sunday) concert must bring their tickets stub tomorrow to be allowed entry the concert.

For those fans who cannot attend the concert on Monday, the refund policy will be as follow:
For those who had acquired the tickets at the HSBC Arena box office and other P.O.S, will be able to ask refund at the HSBC Arena box office from April 4th onwards, with the tickets stubs.
For those who have acquired through Call Center or internet, please keep the ticket stub and make contact with [email protected], or phone number 4003-1527, from April 4th on.

The band are naturally very sorry for any fans that can’t return tomorrow but promise a great and safe show tomorrow Monday for those who do.

HSBC Arena and the band thank the incredible fans for their understanding of this difficult situation and their cooperation. As much as the band wish to play for their fans the safety of each one of those fans is always paramount. Iron Maiden look forward to a fantastic concert tomorrow.