Why did Ye Rongtian and Tian Ning break up in TVB Genesis?

Three years ago, when Tian Rong went to the mainland, he met Tian Ning, and they soon fell in love. At that time, it was the low point of Tian Rong's career that he went to the mainland to do business. He and Tian Ning stayed in the mainland for two months, and then took her to Taiwan Province Province. On Tian Ning's birthday, he got a call from his business partner and immediately rushed back to Hong Kong, leaving only a note for Tian Ning saying that he would come back to find her. However, the business delayed him for a long time, and then he went back to Taiwan Province Province to find Tian Ning many times, with no result. This relationship will end in vain.

Later, Tian Ning lived in Taiwan Province and met Zhang Zili. However, this process is not described too much in the play.