Proctor was hanged in the crucible for refusing to do what

Proctor was hanged in the crucible because he refused to confess to the lies on the appearance of Rebecca.

Explanation:

This is because his conscience is affected and he refuses to agree that he saw Rebecca and the others doing conspiracy with Devil. The character known as Dan forth also tried to pressurise Proctor for signing the written testimony of his guilt. However, proctor refuses to do so and thus he was hanged in the crucible.