Can't sychronize my sequences because "a match could not be found"

[matthewfang1999]

Hi, I'm currently trying to sync multiple sequences that I created from different videos. However, after I tried syncing them (with track channel 1, 2 or mix down), I got the error message that "a match could not be found." I've attached a screenshot with my current setup. How can I address this? 

[Ann Bens]

Its just half a screenshot.

Show us the entire timeline.

[matthewfang1999]

Sorry about that. Here's the full timeline

[Jeff Bellune]

It could be because you're trying to sync A1 and A2 to V3 and V4, and A1 has no audio with which to sync.

[matthewfang1999]

Hi, thanks for the response. I tried making the change but it still does not sync! 

[Ann Bens]

Select one video with audio to sync to the other two audio clips.