Before going to sleep, Chen Ningxi replayed the video call with Cheng Qiaobei in her mind. Although they had been all smiles throughout, there was something off about his demeanor, and his eyes occasionally darted away, as if he had done something to let her down. Combining this with the current state of their relationship, the only thing that could be making him feel guilty would be the meeting with Cheng Qiaobei's father.
It appeared his father was reluctant to meet, and reluctance meant disapproval. So, he felt he owed her an apology, and with this logic, everything made sense.