Complex sentence: Their suspicions only grow when the Senate grants Palpatine a vote on the Jedi Council by appointing Anakin as his personal representative but the Council refuses to grant Anakin the Jedi Master rank.
Split into simpler sentences: Their suspicions only grow when the Senate grants Palpatine a vote on the Jedi Council by appointing Anakin as his personal representative. However, the Council refuses to grant Anakin the Jedi Master rank.