With special reference to the last Act (Act V) discuss why it is said that the rebellion was a failure.

The rebellion was a failure because even though Henry took the throne, his rule was a precarious as his pedecessor's. Richard's murder puts Henry in the same position Richard was in at the beginning. It doesn't matter how Henry seized the throne, because as long as Richard remained alive he could say that Richard had ceded the power to rule over to him. With Richard's death, however, this is no longer possible. As a result, Henry must now defend himself against the same accusations he leveled against Mowbray, namely those of treason.