AI will barely ever accept ceasefire if you share a border with them. You can have them completely surrounded with only 1 city left and no army and they will still see no need to accept a ceasefire. Sometimes, VERY rarely they will just accept out of the blue, but 99.9 times out of 100 they will flat out refuse.

However, if you don't share a border they will accept almost all of the time. For example, play as the Romani and kick Epeiros off the peninsula. After that they will accept a ceasefire because you don't share a border. Try to acquire one before kicking them off the peninsula however and you'd have more chance of getting a rock to shit gold coins.