How do I approach this?

Been seeing this guy for 4 months now although we recently experienced a rough patch, we were committed to work through it. Last monday was his birthday and we had an amazing time celebrating.

On Thursday, we had dinner to celebrate seeing each other before we both flew home for the holidays. During the dinner, we both just went silent for no reason and even during the ride home, neither of us said anything. Its been 4 days and neither have us have said anything to the other. I just dont understand 😕