The Council of Trent was called by Pope Paul III (pope from 1534-1549) during the time that the Roman Catholic Church sought reform after the Protestant Reformation. But, this Counter-Reformation did not produce many results as the pope did not wish to relinquish any of his power as some of the abuses were profitable for the Papacy.
Attendance at the Council of Trent by the bishops was poor. Whereas 700 bishops could have attended, only 71 did. In addition, the pope's views superceded any of the bishops', so there were virtually no reforms made.
King Charles V had hoped that reforms would be made that would return some Protestants to the Catholic Church. However, in the first session, the great differences were upheld. For instance, the fundamental Protestant belief that the Bible alone is the basis of Christian faith was rejected. Instead, Scripture and tradition remained as equal authorities, and faith and good works were intact as opposed to Luther's doctrine of "justification by faith alone."
After the many sessions of the Council of Trent, questions on the Sacraments, salvation, and the Biblical canon were answered and the differences between Catholic and Protestant remained so that the Council became more of an affirmation of Catholic doctrine rather than any compromise or attempts to reclaim Protestants to the Catholic faith. In fact, when the last session began, all hope of conciliating the Protestants was gone; nevertheless, there were reforms made within the Catholic Church, such as the forbiddance of selling indulgences. Curiously, the Council of Trent made no pronouncements on papal authority, which was an important issue for the Protestants.